Do you know this guy? Is this atypical of him, like he's usually the nicest guy in the office, but get him near a cyclist, and he goes all neanderthal?

I'm willing to bet that it's not just cyclists. He's probably as easily angered by old ladies crossing the street, little kids coming off the school bus, but he'd look like a a$$hole is he expressed his true feelings about them.

In any case, the best response to him during his tirade is "boy, it must suck being you" said with a look, not words.