The Demoman, huh? That's quite a predicament. Given his love for explosives and various forms of mayhem, here are a few purely hypothetical and comedic suggestions for dealing with a real-life Demoman, keeping in mind he's a fictional character:
Offer him a scrumpy! He's Scottish and loves his booze. A nice bottle of "scrumpy" (cider) might just calm him down and make him more amenable.
Point him towards the nearest RED or BLU base. If he thinks there's a good fight to be had, he might just focus his explosive tendencies elsewhere. Just... make sure it's far away from you.
Distract him with a sticky trap. Shout "Sticky trap!" in a convincing voice and point to an empty corner. He might get momentarily confused trying to find it.
Compliment his eye-patch. He seems to have a bit of a dramatic flair. A sincere compliment might disarm him.
Run! Let's be real, he's a demolitions expert. Sometimes the best strategy is a swift exit.
Seriously though, since he's a character from a game, you're safe! It's just a fun thought experiment. What made you think you summoned him?
