OK, I'll need to see a source on increased pollution. I really doubt that a motorcycle is putting out more pollution than an average American-size vehicle. For example, my sport bike gets 59MPG, and I've owned multiple bikes that got >100mpg. Even without a catalytic converter, how is that more pollution than a single commuter driving in a truck or SUV getting 20MPG and likely shedding more road and tire particulate due to the increased weight.

Edit: although the noise thing is valid, I'm perpetually annoyed with the "loud pipes save lives" crowd, that's obnoxious.

This is absolutely false. Any motorcycle you can buy in the US is required to meet both noise and pollution standards.