This happens quite a bit. I think quite often, people (myself included, occasionally) forget there's a person behind the character. We should talk trash about the character, but not the person behind the character. But all I know is every time I see Waltonbrand running around throwing out heals in a fight, I'm always like 'Get that d bag! Focus on my target!' =P
There are some people who are just hateful little trolls and, like you said, feel it necessary to launch personal attacks against others because they just have a cold black heart and need to make themselves feel superior somehow.