Not because I think Steve would hurt anyone directly. But at any moment he may be like "would you like to see this deadly spider I've got in m'pocket?" And then pull out a spider that even spider scientists didn't know existed or some shit. He would never let the spider hurt you, but you'd have a heart attack anyway.
The people you know well enough to trust them are close to you but unknown to others, so other people wouldn't really appreciate your unswer if it was just some common unknown people. You mostly cannot bet on the character of celebrities, because you don't know them personally (see Gaiman). Fictional characters are known by many people and their personalities are nicely described in the books, movies, whatever....