Theories aside, you have a solid point.
Science celebrities (DeGrasse-Tyson, Sagan, etc) would be awesome proponents of science... if they would stop yapping politics. Seriously, scientific discovery and history are wonderful things. Enticing folks into wanting to know more about our world and universe is an awesome thing.
But... when you have some scientist-turned-celebrity yammering on and on and on about some purely political viewpoint (and worse, misrepresenting opposing ones and falling victim to even the most basic of logical fallacies), then it sucks.
A good example of a science celeb? Dr. Michio Kaku. Dude sticks to science for the most part, and doesn't try to recruit political acolytes to gain points, controversy, or notoriety.
But they don't exist in a vacuum. Politicians and religious leaders are shouting all this jargon, and both journalists and pseudo-journalists ask them questions about it, and someone has to respond to it. As the press has recently caught on about, the creationist movement cleverly gamed the system so that their pseudo-scientific views were on a par with mainstream scientific views-- "teach the controversy". There really isn't a controversy. If scientists somehow all refused to respond, then the public would be even more misled, I would think.
They are relatively good but absolutely terrible. -- Alan Kay, commenting on Apollos