Is it ever advantageous to pretend to be the "hidden" team if you are on the majority team?
Specific games can differ, but generally in games like these the "bad team" all know the members of the bad team. Therefore pretending to be a bad guy only decieves your allies, and convinces everyone that you are their enemy. 

Neither of those will help you. You're harming your allies' ability to make accurate judgments while not affecting your enemies, and you're making our so that no one will listen to you.