ExH wanted a dog. Well, he one day announced (out of the blue) that he would be getting a dog, and if I didn't like it, I could f* off.
At that point, I was working full-time, and juggling looking after 2 children/taking them to childcare etc. He was drinking (I knew about that, I thought he was addressing the alcohol addiction - turns out he wasn't), taking drugs (unbeknownst to me) and was a complete mess. I told him that if he did get a dog, I'd have the dog rehomed and he could find another place to live. He decided against it. I don't have a problem with dogs, but I knew that all the work involved with looking after it would be left to me, and I had enough on my plate. I was also struggling to keep afloat financially. It would not have been fair on the dog at all.
In our case, had he been sober/clean/responsible, I wouldn't have had an issue with having a dog. I would have trusted that he would look after it/walk it/feed it whilst I was at work. ExH and I have separated now, and the kids have mentioned having a dog or cat. Again, all very nice, but we're all out of the house for a large chunk of the day (they're at school and I'm at work). I've explained to them that it wouldn't be fair on the dog, so they understand that. I have said that every few months we can re-look at the situation. We do have a snake (my snake - I've had him since 2000), so I've suggested that they research all the work involved with looking after dogs/cats/reptiles and make a decision based on that. I figured that would be a good way to talk things through and come to a compromise of sorts. :)