as best i know, in general, when we have 0% fold equity (which we most likely do here) and <50% equity, we are better off flatting than raising, which essentially puts more money in the pot against a range which we lose to more often than we win. thus i think i prefer flatting, especially when villain sized his bet so terribly. that said, this is the most trivial spot in the world. preflop iso is standard, and the only -EV move postflop is to fold (even if he open-shoves the flop, we are getting 2.5:1, needing about 28% equity - we're never folding)