Actually, the origin of the term "streetfighter" in reference to Motorcyclists supposedly goes back to post WWII when cafe racers came about.
The pilots who were coming home from war were adrenaline junkies in the UK and European Ally nations. A lot of them likely had post traumatic war syndrome, though that wasn't known at the time.
Anyhow, these guys were used to flying dangerous missions with no regard to safety and having drunken fun in the interims... thus, cafe racers came about. The newly returned home soldiers would buy bikes because bikes were fast, fun, and dangerous. They would modify the shit out of them to make them faster and they would run them like there was no tomorrow. The fad took off with the youth and a culture was born when it blended with rock and roll music.
These guys were fighter pilots. That was their life. They were no longer piloting bombers, and now they piloted these modded up streetbikes.... so there were references to them being called "street fighters" in some UK papers.
I'll try to find the article about it. It was the weirdest thing. There were actually examples of articles from the period where they were referred to as that.
(In the US we didn't have the need for bikes that were designed to maneuver the curvy streets like in Europe. We had long straight stretches of open road. The same type of soldier returned home here, picked up a Harley instead of a BSA/Triumph/Norton/Vincent and they'd cut everything off of it (chopping?

) to make it quicker and lighter for speed. They had no need for the handling though. Thus came about the roots of bobbers and choppers.)
At least that's from what I've read around....