I agree, it's all cultural. If we'd look at the facts, pigs are at least as sentient and intelligent as dogs. If we were to make our laws just from ethic principles, it would make sense to either:

a) ban how we currently treat mammals in factory farms; though there would still be some space for whether eating mammals is fine or not.

Or:

b) acknowledge that we don't really care about mammals and just treat them as things. Then it should be fine to eat dogs and cats, too.