The biggest flaw in advertising and/or promoting veganism and vegetarianism is focusing only on animal rights. People separate animal and human welfare as if they are two different things; they are not. The welfare of animals and good care for livestock is essential for our own safety and health. I'm sure everyone would agree that cows bred on farms with fresh air and 'normal' life are healthier to eat than those stuck in cages, suffering from diseases and pissing themselves. And the biggest problem of meat industry is the fact that it is an industry; meaning, it requires slaughterhouses because otherwise, it couldn't fill the demand. And the reason for such demand is ... well, we're humans. We love to exaggerate when we have the opportunity to do so. And exaggeration is the problem. Despite having a natural capability to eat and digest meat, we were never intended to eat it three times a day, seven days a week. We do it because we can, not because it is necessary (or healthy). I honestly have no problem in people loving to eat meat; that's perfectly normal. However, eating too much of it heavily damages our own health and the planet along with us. That should be the main concern, not focusing on animals and thinking people will suddenly start caring about pigs. They won't, because pig welfare is not the most important thing that gets screwed up in the meat industry (nor is it the most important problem of the modern world).
I don't eat meat, by the way, and I'll just note that I absolutely despise these labels (vegetarian, vegan, whatever). It brings so many stereotypes that I try to avoid using the V-word because people immediately assume I'm some sort of a animal rights activist whose only reason for not eating meat is my love for animals. I won't lie; ethical reason are present in my decision, but they are not the first or the main ones. Also, I am not against eating meat; as I said, that's normal. What I think it's not really normal (or good for anyone) is exaggerating, and the (western) world exaggerates.
Humans were vegetarian in majority throughout history; it is only recently, with the beginning of industrialization that we switched to meat-heavy diet (and that's counting just the western world. Also, the only time when 'we' ate so much meat was when 'we' were Neanderthals). But still to this day, healthiest people are the ones who eat little amounts of meat. I believe that's what we should strive for. When animal rights activists fight against eating meat and believe that humanity will one day completely stop eating all kinds of meat, they are not really being realistic. People will always eat meat. What we can do is make sure that we eat it moderately, which will in turn improve the quality and safety of it, and while we're at it, there will certainly be some sort of artificial meat industry one day (when it gets better, you won't even know the difference). And even then, some people will not eat meat anyway. I don't think all people are the same or have the same needs. Some people need meat, but I am extremely sceptical at the fact that people need that much of it. That's just exaggerating because you can. And well, it's not my problem anyway, but it would be foolish to deny the fact that exaggerating is harmful. You can not care about it, but you can't, with a straight face, say that it's not harmful (to humans, animals and Earth). So yeah, essentially, my opinion is; eat what you like, don't be an asshole about it and do try not to consume in one meal more than some people could survive from for a week.