I wouldn't plan to bring a dog home without asking for his consent first. For example, Abrams. I wanted a pup from an earlier litter, but Michael couldn't emotionally handle the stress of a pup plus finishing school, so I waited. I was upset, but I knew it was for the best.
That being said, if I found a dog on the side of the road and brought it home, he'd get over it.
Pocket pets are a little different. I may ask him if he minds, but in the end, unless it is a legitimate reason for not wanting one, I'll probably just get it anyway because he won't really care. Barn cats will fall under this category, too, because he hates cats and will never okay me getting one. But once I get one, he won't care.