You're actually questioning whether you should contest this??? Wow.
In court, simply ask the other guy to explain HOW you managed to break his mirror. There's NO WAY he can give any answer that doesn't implicate him ("I was trying to hit him with a bat," "I was trying to pass him when there was no room," "I was trying to run him over," etc.).
Ask why in the hell you're even IN court (or were arrested in the first place) when you're on a bike and a guy is trying to run you over so badly that he was willing to drive the wrong way on a one-way street.
Man, I would get a lawyer and milk money out of this! Heck, what a story for the news too.
You should be lucky you "only" got some road-rash.