Most often, the actors who speak out (as opposed to running for office) are being questioned about their actual knowledge on the issues, and their use/abuse of their celebrity status. Tom Cruise as an authority on psychology? Puh and leaze. And Chuck Norris dissing McCain as being too old to run for President, when McCain is just four years older than Norris? Laughable.
I don't think Tom Cruise is a viable example here, since his meltdown has no political overtones/connotations. Excessive celebrity is nothing more than that.
I have to say, however, that I have to question the critics' actual knowledge of the issues. All I see is "spin". It's one thing to carp about an actor getting "press" because of his celebrity, but most of those who carp do so because they don't want anyone using whatever celebrity they have to speak out.
And the lunacy of declaring someone's career as being DEAD because he speaks out against the war is a sicko's attempt to shut people up and prevent them from expressing opinions (I don't think Alec Baldwin or Sean Penn ever noticed their careers were dead.