Oh my jeezus. Really?? You have a long life ahead of you sweetheart

Well when you think about it, it makes more sense that whales are considered fish I mean look at them they swim they have fins and their body is shaped like a fish

Educate him on what it means to be a mammal. Mammals possess a neocortex in the brain, mammary glands to feed milk to their young, hair, and 3 middle ear bones, they often live birth their offspring as well. Whales and dolphins possess all of these things, therefore they are mammals. If he's surprised by dolphins and whales being mammals, you could also really throw him through a loop and tell him that platypuses, despite laying eggs and being partly aquatic, are also mammals.

Google.

Haha Hi guys. First I want to say thank you for getting my FML published (well almost). And my boyfriend does know whales and dolphins are mammals, he also is a jokester who knows how to get on my nerves. As an animal lover who is majoring in animal behavior and pre-vet, I always tell him little fun facts and stuff like that. This particular time, I was saying how it was crazy that blue whales are the biggest animals on earth, yet we very rarely see them. He then made a "whales are fish" comment and I corrected him, but then he kept making it and I continued to defend my answer, but he was using the whole "Whales are fish because I said so. Also dolphins". Needless to say I was pretty pissed off but it's all good now. Thanks!