Was it the gesture itself and to whom it was directed, OR was it the commentary from the media that said Trump was "mocking a disabled reporter" which made you believe he is a POS?
Because in reality, apart from political commentary Trump used that same gesture to resemble the agitation and confusion of many people whom he has spoken against and he has used that gesture for years. So, if you didn't think Trump was a POS back in 2005 or when he "mocked" bank presidents, a general, or Ted Cruz in the same manner, you are doing/feeling/believing what you were told to.
Very good explanation with supporting facts and timelines. Too bad people still won't except it and will probably just mock you instead of refuting the premises and logic you provided.