Sure they are, and just like you and I, they're free to make whatever boneheaded choices they want to.
The Robertsons have a television show. It's a business. By attending the White House correspondent's dinner, they came very close to touching a third rail in the entertainment business, which is partisan politics.
I haven't even voiced an opinion on what they did. I've only made the observation that it was a poor business move on their part, which it was.