If he really wanted to test a colubrid's venom, he should have done it at feeding time, since they seem to release the venom when catching prey rather than in defense
But the only hognose snakes I've handled have been so small that even if they wanted to bite me they likely couldn't. I have yet to have any of them even try. They're just little
The garter snakes on the other hand...
Much more likely to defend themselves by biting.