"Not a crossbow, a proper bow"....good old bow snobbery in full effect as usual.....

Crossbows are still used by many armies across the world for various reasons, I don't get why archers are so down on them. I've got an Armex Titan(200lb draw, claimed 380fps) and use it safely in my garden using a Third Hand Rag Bag as a target. I'd argue crossbows are more safe than the average PROPER bow....my neighbour has a recurve bow and has done archery for years, he can't hit 2" groupings at 40yards. I can....
(Ah, that's why archers are probably down on them...I can consistently achieve the same results with a £245 kit that an archer would need to spend a grand on, like a Hoyt?)

Anyway, I digress....As long as you both have effective and sensible backstops and don't go out firing/shooting when under the influence of anything then you should both be ok?

If he has a high powered crossbow, look at what he's aiming at and it it isn't capable of stopping the arrows(they're not technically bolts unless they have no fletchings/vanes), point it out to him and if he gets his back up and won't see sense then maybe give the plod a phone.....they may be able to "advise" what he needs...

Regardless of our choice(s) of bow/rifle, responsible usage is the most important thing....