i don't assume that people bet out with trips. Put him on a medium pair that doesn't want you to hit w/ overs and raise the flop. Most cap w/ QQ+ preflop so your probably good. You miss too much value by just calling down. If he reraises you on the flop and his aggression is really low then you can lay it down but only if you know your opp well enough to be sure that your beat (basically just call down).