I would say that many men do not understand what constitutes rape. For example lying and coercion to get what you want. So I might not believe him since there have been many studies done in which men will say "I'm not a rapist" but when asked if they will pressure a woman into sex they say yes. So, in general, consent is not well understood.

So my ultimate thought is that no man will admit he's a rapist. So the only thing that would really be helpful is if I knew him well enough to know he's not.

For example, my ex and I were having sex one time and I said "ow". He was off of me and soft within a second. Obviously I trusted him before this moment, but his response to my simple exclamation proved to me (again) that he would never be capable of rape.

So, no, a simple proclamation that "I am not a rapist" does nothing to help the situation or to create trust.