I'm going to reveal someone's political affiliation
Why do you want to expose this person's political beliefs?
There's a few reasons behind it.
If this person has chosen to keep their political beliefs a secret, then it is not your duty to tell everyone their beliefs. As long as they aren't causing harm to themselves or others, then people's beliefs, and who they tell about them, are none of your business.
They have shitty beliefs that needs exposure.
You personal judgement about what they believe is irrelevant. You don't have the right to talk about something they want to keep private.