People get so worked up because of the nature of animal care. If you are a caring, responsible pet owner, you will be hard pressed not to get emotionally invested. I, for one, LOVE my fishies and am not shy about saying so.
I don't know about drummers, but it's always touchy when pet owners try to tell other pet owners how to do things. It's kinda like that lady at the store hitting her kids. You know everyone wants to tell her not to do it, but it's rude. Some people would go ahead and tell her off anyway for the sake of the children. There's not that kind of stigma attached to pet ownership. If someone thinks they have a better way of doing things, they go ahead and say it. Pet owners are probalby some of the most self-righteous people I can think of.
But maybe drummers get as defensive when another drummer tries to tell you how to play! I don't know. You guys are artists, so there's probably respect for letting everyone do it their own way.
Anyway, that's just what I came up with, in answer to your question, in the past 10 minutes or so... Although I've certainly thought about this one before myself.