I've witnessed this bias firsthand, I have my own website with sci-fi wallpaper that describes the weaponry of space battleships. Google's adsense ads get all squishy when I put an adsense banner on this page. I get ads like "tsunami relief" and "students creating peace" and "world peace". I want ads related to Battleship Arizona on this page, not a bunch stinking hippy crap. Anyway, here's the link to that page:
Space Battleships and their weaponry
I'll keep it like this for a couple of days, but I'll change it to get a better quality ad. The thing is, boycotting Google is not an option for me, it's a major traffic generator to my site and their hippy-crap affects my business.