The best source and the best citation is his own words. If you read the interview Waters says "(...) if you believe artists should be mute, emasculated, nodding dogs dangling aimlessly over the dashboard of life, you might be well advised to fuck off to the bar now (...)". If you like to eliminate his political views and see him "only" as artist you don't have idea what are you talking about. So yes we have to follow all his political views as well.