Maybe it's just me but I see a lot more liberal leaning comments on here than I do libertarian.
It seems to be pretty even split IMO. It depends on your personal bias - if you lean in X direction, comments leaning in X direction will seem "reasonable", therefore not trigger your "oh crap this person is a Y" alarm. Since the human brain isn't really wired with an "all is as expected" alarm, it tends to not notice these things.
But wouldn't "reasonable" comments trigger an "oh crap this person is like me" alarm?
No, for the same reason that pain is more memorable than pleasure.
With the high localization of individuals in SF, NYC: you're probably not wrong.