What you've got to remember is, parents may act like they don't care about you, under difficult and emotionally challenging circumstances, but the person who has "come out" is still their child, I strongly doubt they'd do something stupid (there's not much they can do, and if they do do anything you'll notice, obviously if it's physical injury) but just make sure that he knows you're willing to listen to him and as sad as it sounds, offer him a shoulder to cry on.

I think he's taken a big step, coming out gay, he's just got to live with it, and he must've expected this to happen as I'm sure him coming out was fairly well planned.