Cause people are people even over the internet?
Ok, I'll give a small theory I have on the matter.
This may have varying degrees of sanity and/hilarity as I do not profess to be a psychology major, nor an astro physicist.
The world we live in is very hard to define. In order for our brain to make sense of all the chaos and random information it needs anchors, things that we can look at and point and say "That is [name]". Basically the argument of "An apple isnt an apple, it's just a round some what spherical red thing." But even those breakdown with enough scrutiny really. ""Are they still apples if there is no one left to speak of them?" ect.
Anyway, I'm getting off track.
That basic idea, that your brain needs concrete things, or ideas to latch onto, to declare what the boundaries and definitions of your reality are, extends to entertainment media as well.
Now when you attack or challenge something like this, that is basically attacking a persons perceived reality.
And I've found over the years that it's playing with fire.
(Try telling a evangelical christian god doesn't exist, or a militant atheist that he does)
Take into account that media often times helps us develop, helps s grow is there for a lot of good times and a lot of bad, in some weird way becomes a part of you, whether superficial or otherwise, it's not surprising people tend to have the knee jerk reaction they do.
I'm not saying we should let our baser impulses rule us and not try to be nice with each other in regards to common likes and dislikes, I just think it's a bigger part of a humans psyche than most realize.
I have no idea if I communicated what I'd hoped to or if I sounded like a stark raving lunatic, but if so, I hope you at least got some food for thought out of it. ^^