You seem like a very sensitive creature. I really hope that you aren't serious.

ZOMG, I saw somebody masturbate!!! My life is ruined!!! He must have STDs because he'd do that!!!

Would you rather he'd have done it across from you on the MAX or hiding in that corridor? The homeless gotta jerk, too, prude.

"You smiled and winked, repeatedly making the "sssshhhh" gesture with your free hand" Repeatedly? Meaning you watched him long enough for him to do it more than once?