You're right, though I wasn't thinking of penalties outside of Congress. Congress can only go so far as to expel a member, right, or can they put a sitting Representative up for impeachment? Assuming they can, I suspect the fallout from that would be...impressive.
More likely is that the party leadership would not let them on any of the important committees. Or they may via backchannels fund a primary challenger.
The House Intelligence Committee is part of the house, so they are allowed to penalize Congressmen for speech.