I thought what Hung Jon meant when saying, vulnerable, is usually guys tend in public to be somewhat "macho" and "he-man." Yet, when you read other threads on this sight about things like peeing in public restrooms, or taking a shower in a gang shower room, or undressing infront of other guys in a locker room, etc., so many guys act like they want privicy...kind of staying away from the situation of "exposing" theirselves, if possible. Yet in the gay movies, these guys drop everything, every thread of clothes; they hold back from nothing and go as intimate as can get which goes against the "macho, he-man" image that men are thought of in general to women and a lot of straight men. That's the kind of vulnerable I understood from Hung Jon. I heard the gay actors do not receive near the pay that the porn women make, either.
I'm not saying either way is bad or good; just describing what Hung could have meant. When you watch gay movies, one of the guys plays what the usual women's part is in accepting a man's cock into their body. That's vulnerable, I'd say... in front of a camera to be marketed for others to watch.