I'm not going to weigh in on pets particularly because I don't know enough, I'm also not vegan. I do however want to remark that you can sense the meat eating guilt and reactionary emotional defensiveness in a lot of this stuff. People feel very attacked and very defensive.
There is an underlying feeling deep down that it is wrong but because they personally enjoy it and get happy hormones when eating the topic triggers a massive emotional response.
Speculation: Eating food is probably one of the only times some people truly genuinely feel happy and is responsible for the massive defensive reaction when anyone suggests food habits should be changed. I suspect that the non-vegans that do not react poorly to the topic have much stronger sources of happiness that aren't food.