Pretty sure I'm not bulletproof. It certainly would have made everything a lot easier, though. Dammit, this sucks. I've been walking away from bullies my whole life. I don't fight because I don't want to hurt anyone. Why can't this cop understand that I ran for his sake?! I didn't want to be in a situation where I'd have to hurt him! Even after he hurt me, I never touched him! Why is he lying?!
As you said; in all likelihood the guy is a coward and a bully (same thing in my book). Whether that's due to childhood trauma or just inherent moral bankruptcy is another issue, and probably isn't relevant. It's obviously a serious issue that such people are attracted to careers in law enforcement, and the system seems to accept them, but I think it is becoming less acceptable, and more frequently exposed by the media, which may work in your favour. Ultimately one would hope that it's a small group of people taking advantage of the system, and not the system itself that's at fault here. If that's the case, then you should be able to sort this out to some degree. Asmodeus' advice (i.e. securing dashcam footage) would be worth following I think, and I'd urge you to get in contact with civil rights groups, as essentially your civil rights are being infringed upon here, and they exist to prevent that; at the very least they should be able to give you informed advice, and they may even provide legal support. It can't hurt to look into it. Reading your account of events, it seems to me you haven't done anything wrong, and I'd like to believe any reasonable jury would come to the same conclusion. It's not like you have any previous (I assume), and you weren't under the influence, so it makes no sense that you would've attacked a cop for pulling you over on something as trivial as riding without a light; I wouldn't have thought the cop's version of events would hold up to much scrutiny in a court of law. Lastly; I'm not sure if there's anything I can really do to help, but if there is, you only have to name it.
*puts on a top hat and monocle* I say! Quite! Pip pip cheerio! What ho, old bean! Quite! I say! Earl Grey! Quite! Indeed! Pip pip cheeri... *pries off top hat and monocle* What the hell just happened?!
*puts hat on Alice* "Bob's your uncle! Oy! This's pants! Gobsmacked! Ye plonker! Fancy a butcher's?! Oy!" *takes hat off Alice* "If you ever do that again I will disembowel you through your nose."