I could translate what Trump did as generalized mocking just as easily as mocking a disability. Only Trump knows what he was thinking when he did that. Had Trump taken it a little further by offering insults directed at the individuals disability, I'd have a different opinion. It is also possible that my ignorance of the reporter being targeted has influence over my opinion.
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I don't think the details matter much, in either case it was unnecessary and childish. Neither scenario should be considered acceptable from a political figure. There are times when being "PC" should be waved to engage in meaningful but difficult conversation. It should NEVER be used as an excuse to insult /denigrate a person or group of people though.