This is how I think of it - you can say "I told you not to go out and be a hero. And what do you do? You go out and be a hero." But you can't say "I told him not to.... he goes out and *bes a hero." But it feels like it works, because "goes out and is a hero" has a different connotation (and I also wouldn't say "you go out and are a hero" in the analagous example above), as well as rephrasing it with other verbs such as "goes out and acts the hero." It feels like there's just this gap in English where that verb form should be, but I don't even know what to call it.
I guess I don't have any specific question to wrap this up with. Just... discussion?
ETA: It's not that I don't understand what he meant -- it's completely intelligible, just non-"correct," and I've done the same thing myself in different contexts (I didn't provide other examples because I couldn't think of any off the top of my head; if anyone else can think of any, please do).