The anonymity of the internet doesn't help. I have fallen prey to that, and I try really hard not to. It's hard to punch someone through a monitor. Makes you feel like you can say anything without risking any limbs.
I've met very few furries that act like that in person, though. I'm sure I'll meet more if I widen my sample size.
"It's not tragic you have Merlin's Magic!"
"TROLLS!"
I'm not sure if you are aware of this, but there is an effort by furries to influence the public's opinion on the fandom both ways. I can think of furs that want to help the fandom's image (encourage mainstreaming). I've can think of furs that want to sterilize the fandom so people can't think poorly of it (also encourage mainstreaming). I can think of furs that want to hurt the fandom's image (discourage mainstreaming). You probably ran into group number two. These things happen when you get a fandom.
Some people had a bad day and really shouldn't be interacting with others at the moment. "If you don't have anything nice to say, don't say anything at all." kind of thing.
As for word choice, "pedophile" is in the same bunch of name-calling as "Hitler" these days. A good friend told me this once: He swears because, say, he stubs his toe on the door. He's in pain, so he does something quickly to do something other than focusing on stubbing his toe. I yelp or growl, he swears. It's a reaction with a widely accepted understanding. He doesn't want to spend the time to say it more eloquently, so he lets loose some foul literature... a reflex.
Here, this person may have combined one or more of the above reasons for disliking your picture and this reflex reaction... they wanted to let you know they didn't like it, but they didn't feel like typing it out for whatever reason, so they swore at you.