Word for someone using their fame to push their personal agenda

single word to describe someone famous who uses their fame to push their personal agenda. Example is sports or entertainment celebs pushing their political/environmental/equal rights agenda

Ed (a famous sportsman) is a xxxxxxxxxx for using his fame to promote his political views

I have done many searches revolving around one using their position to advance their personal agenda. The closest word I've found is opportunist - although that doesn't seem to describe the extra influence that fame contributes to it.

The common phrase I've seen for this is "celebrity activist"--see news examples here at Huffington Post. Google searches also return this phrase in tabloids and pop culture magazines.