Why not? If my partner didn't love my dog as much as I do, it wouldn't even get to the point of marriage.

Wanting the dog as best man? A little weird, but forgivable. Threatening to end the engagement over something so juvenile? Unforgivable. Feels like this is unlikely to be the last time you hear this sort of threat. That's when you say "Go for it."

Welcome to the first compromise of your married life! Seriously though, maybe have a best man who will walk with the dog down the aisle so you get both. Also tell him to stop being an overdramatic dick. He should discuss it without throwing a stupid ultimatum at you.

I know it's extreme but he has a point. Now hear me out! If you guys have such drastically different ideas of the dog's importance in your lives, it will be a constant point of contention. You will always fight about how the dog is treated, what he's included in, etc. Now if he's just being silly though, sorry he's saying stuff like that.

That's going to be a fun wedding!

Maybe you should threaten him back.

But the Best Man is supposed to organize the bachelor party. What would that entail? Licking their balls and eating poop they find in neighborhood yards?

I don't see the problem... The dog is likely a better person than any human you'll ever encounter. Considering he's a better person than most, why shouldn't he be the best man?

Bow wow that sucks

Unleash the hounds!!! And have a great wedding!