I believe that they exist. That does not indicate a belief in their accuracy.
Are you you reluctant to explain how you arrived at your conclusion that the usual responses to the question ""Why are you a Trumpist?" would be "Who told you that I am a Trumpist?" or "What made you think I am a Trumpist?"
If so, say so.
If not, please explain whence you derived that expression of certainty.
What other answers would they be?
"I am not a Trumpist."
"Are you retarded?"
"Get away from me you fool."
"Are you for real?"
"Why ask that dumb question?"
And so on.