There is a law being proposed in Philadelphia that would allow the confiscation of bikes without brakes. To the layman, a bike without a brake seems ludicrous - how do you stop? But a fixed gear bike in effect has a brake called "your legs" and by that I don't mean Fred Flintstoning it. Granted if you aren't very good at it, or your bottom bracket brakes, you're screwed. This applies to cars as well, and for all the rhetoric the relative risk posed by fixie riders is nominal.
Meanwhile, in the last two weeks the Bay Area has seen two incidents where a motorist killed other people while driving at a reckless speed. In Menlo Park , someone ran a stop sign at 70 MPH plus and killed a 6 year old girl. In Sonoma a mini-cooper going 100 MPH resulted in the death of 4 people in the car he hit - and the driver of the cooper.
70 MPH is way out of line on Bayfront in Menlo, but 100 MPH is beyond the speed limit in the entire US. Yes - even in Montana. If it's illegal to drive a car that fast - why allow those cars to exist? I know some people will drive their cars on the track and are allowed to go who knows what speed there - but that is by far the exception and not the rule.