Because I haven't yet gotten it through my skull that some forums will practically lynch you for mentioning it, and because it doesn't seem any weirder than any other subculture. I'm a bit curious as to why people are still so intolerant of it (maybe they generalize and think furry consists only of the extreme versions of the culture). But unfortunately I can't give the usual reasons for defending it either because those too get attacked and sound kind of hollow. Something Awful likes to point out one of the most ridiculous examples being a picture by TaurinFox I believe of a fox shedding a tear, USA flag in the background (or something patriotic), and a message basically saying that one day furry culture will be accepted. If I had to give a term to it, it'd be "taking the culture too seriously".
So it probably helps that I laugh at the typical furry jokes, at furries consistently being called worse than other groups, etc. just so I don't find myself getting too ingrained into it. I'd still like to know why all the hate, as I thought the matter and all the usual arguments had been dealt with long ago. Or I could, you know, just try not to mention I'm a furry and to stop before a furry flame war breaks out.
And sometimes I like taking a glance over at forums that flip out over inappropriate furry pictures because they get the best "what the f***! I can't unsee it!" reactions from other people. Even the sick, depraved stuff can be very well drawn and/or surprisingly creative. Even though to find enjoyment in it you must first be the one going "what the hell" and getting nightmares. It's one of those things you get desensitized to.