Well, on one hand you gotta think of how a real person would respond to such brutal and inhumane torture, and it would likely devolve into ceaseless screaming: even Solid Snake, a combat veteran with nerves of steel, screams once tortured, and nobody thinks of him as less of a man because of that.

Then on the other hand I'm rooting for Ian, and for story purposes having him deliver a bit of banter to Lorenzo's face is really gratifying for all the shit he goes through. In this case though, I feel like the system's set up so that Lorenzo could hear Ian speak, in the hopes that he would beg for his life and for the torture to stop like the ultimate douchebag he is. Of course, Gnar's got the ultimate authority on the decision of whether or not Ian could say anything during the torture.