I would fight it just for him being a prick. As long as you do the research, have a good defense planned, present yourself with respectable confidence, you may actually win. I fought a suspended license violation just because the cop was a prick. I had no attorney but have a good grasp on criminal law and ended up getting the case thrown out. The prosecuting attorney was pissed because he just lost to a couple of "thugs". As long as your defense has merit you have a good chance of getting it thrown out.
How did he know if it was you bumpin? He was driving the other direction on a busy road. There must have been many more cars around you at the time.
Was his window rolled up? How could he be sure it was you?
Was your stereo on when he walked up to the car? Just because someone owns a gun doesn't mean they are the culprit of a crime.
Did he see your speakers? If not, put some shitty ones in and do a demonstration. Make sure they are bad enough that it puts doubt in the judges mind.
Biggest thing is, don't show contempt or anger. Present yourself professionally and a lot of the time the judge will find it admirable. Don't argue mute points such as Harleys and such, this makes you look guilty and are trying to defend yourself. Only argue the technicalities of the case at hand.
Hope this helps. //content.invisioncic.com/y282845/emoticons/wink.gif.608e3ea05f1a9f98611af0861652f8fb.gif