Anime dubs are usually haphazard, largely because they're being Americanized by those dubbing and are sometimes receive a half-@$$ed job as a result. To be fair, not all anime are like that and are just as interesting to see in both English or Japanese. But not everything translates well and, because of that, usually result in quirks. People pick up these quirks and it turns them off.
But that's the least of it. Another problem is that people dubbing this have this problem. To them, the term child means the same as idiot, and based on that alone, they think they can get away with anything, or at least make the mistake of treating children as idiots and handle anime with a level of maturity that shows in their work. However, even a child knows if you're cut, you bleed. (Various anime) They'll pick up on things that people will think are too subtle for them to pick up on and talk about it. Worse yet, people who aren't child who are fans of the shows (or at least the Japanese dubs) will see it and think it an insult to the viewers. It is, to be blunt, seen as a degradation of the intelligence of the viewers as a whole and a good way to ruin what some people view as a work of art.
And trust me, some companies do go out of their way to Americanize something once they get their hands on it. 4kids is an example of the extreme. They've replaced Japanese food terms with donuts or sandwiches, or otherwise replacing the foods completely. (Pokemon) They'll take Japanese jokes and turn them into extremely corny and not all that intelligent puns, even on kid standards. (One Piece) They've even on some cases taken characters' reactions and turned them into something that is completely out of context. (Naruto and One Piece) They'll gloss over Japanese cultures, replacing their values with ours. One could argue that this is just to make the material easier to relate to, but at the same time, I think it's a bad idea not to expose kids to other cultures, especially since they're going to be awash in the American culture anyway for what could be most of if not all their lives. 4kids got so bad they even earned the disapproval of the Japanese. You know you've gone too far when you've pissed off another country in the process.
Funimation is also an offender, though they seem to be changing recent years. Still, their older projects show signs of problematic Americanization, sometimes going as far as replacing Japanese locations to completely unrelated ones (Case Closed/Detective Conan). Being a Canadian, I find it embarrassing to see memorable locations from Kyoto being passed of as a part of Alberta.
Voice acting is a problem, too. Sometimes, the actors or actresses will read their lines and sound wooden as a result, just barely trying to sound into the material. (Sailor Moon) Or they'll convey their roles in a way that makes the characters sound cheesy or unintentionally strange. (Kenichi: The Strongest Disciple) And truly, there are voice actors who take great characters and replace their voice boxes with a diesel engine or a squeaky toy. (Disgaea) In it's own way, it's kind of sad, because many of these characters can be truly likable, too.
Race is sometimes a tricky issue as well, because there are plenty of people who all too easily take offense at the slightest quirk. People sued the ones dubbing Pokemon because of Jinx's coloring alone. And once this occurred it started a chain effect that resulted in a lot of recoloring in other animes, including Dragonball Z's Mr. Popo and that one Buggy Pirate from One Piece. Now, I have to admit that African Americans have had hard times in the U.S. They've earned a great deal of respect with what they've endured here. However, I believe that it's not helping the issue if we tiptoe too much around the matter. I mean, what's the point in putting them in anime at all if every instance of them is just going to be glossed over by painting them a different color? Is that not racism as well? I have to wonder.
Getting back to the matter at hand, there are some great dubs out there. Such examples are Inuyasha, Dragonball, Gundam Wing, etc. But sadly, when a person encounters bad or lackluster dubbing it can easily turn them off. It can turn what could've been a good experience into a severely watered down one. Because of this happening on too many occasions for some people to stomach, dubs have gotten a bad reputation. That's why we have so many complaints about it.
(P.S.: I'm not racist!)
But that's the least of it. Another problem is that people dubbing this have this problem. To them, the term child means the same as idiot, and based on that alone, they think they can get away with anything, or at least make the mistake of treating children as idiots and handle anime with a level of maturity that shows in their work. However, even a child knows if you're cut, you bleed. (Various anime) They'll pick up on things that people will think are too subtle for them to pick up on and talk about it. Worse yet, people who aren't child who are fans of the shows (or at least the Japanese dubs) will see it and think it an insult to the viewers. It is, to be blunt, seen as a degradation of the intelligence of the viewers as a whole and a good way to ruin what some people view as a work of art.
And trust me, some companies do go out of their way to Americanize something once they get their hands on it. 4kids is an example of the extreme. They've replaced Japanese food terms with donuts or sandwiches, or otherwise replacing the foods completely. (Pokemon) They'll take Japanese jokes and turn them into extremely corny and not all that intelligent puns, even on kid standards. (One Piece) They've even on some cases taken characters' reactions and turned them into something that is completely out of context. (Naruto and One Piece) They'll gloss over Japanese cultures, replacing their values with ours. One could argue that this is just to make the material easier to relate to, but at the same time, I think it's a bad idea not to expose kids to other cultures, especially since they're going to be awash in the American culture anyway for what could be most of if not all their lives. 4kids got so bad they even earned the disapproval of the Japanese. You know you've gone too far when you've pissed off another country in the process.
Funimation is also an offender, though they seem to be changing recent years. Still, their older projects show signs of problematic Americanization, sometimes going as far as replacing Japanese locations to completely unrelated ones (Case Closed/Detective Conan). Being a Canadian, I find it embarrassing to see memorable locations from Kyoto being passed of as a part of Alberta.
Voice acting is a problem, too. Sometimes, the actors or actresses will read their lines and sound wooden as a result, just barely trying to sound into the material. (Sailor Moon) Or they'll convey their roles in a way that makes the characters sound cheesy or unintentionally strange. (Kenichi: The Strongest Disciple) And truly, there are voice actors who take great characters and replace their voice boxes with a diesel engine or a squeaky toy. (Disgaea) In it's own way, it's kind of sad, because many of these characters can be truly likable, too.
Race is sometimes a tricky issue as well, because there are plenty of people who all too easily take offense at the slightest quirk. People sued the ones dubbing Pokemon because of Jinx's coloring alone. And once this occurred it started a chain effect that resulted in a lot of recoloring in other animes, including Dragonball Z's Mr. Popo and that one Buggy Pirate from One Piece. Now, I have to admit that African Americans have had hard times in the U.S. They've earned a great deal of respect with what they've endured here. However, I believe that it's not helping the issue if we tiptoe too much around the matter. I mean, what's the point in putting them in anime at all if every instance of them is just going to be glossed over by painting them a different color? Is that not racism as well? I have to wonder.
Getting back to the matter at hand, there are some great dubs out there. Such examples are Inuyasha, Dragonball, Gundam Wing, etc. But sadly, when a person encounters bad or lackluster dubbing it can easily turn them off. It can turn what could've been a good experience into a severely watered down one. Because of this happening on too many occasions for some people to stomach, dubs have gotten a bad reputation. That's why we have so many complaints about it.
(P.S.: I'm not racist!)