I'm reading a [New York Times article](https://www.nytimes.com/2018/08/18/opinion/the-slippery-slope-of-complicity.html?action=click&pgtype=Homepage&clickSource=story-heading&module=opinion-c-col-left-region&region=opinion-c-col-left-region&WT.nav=opinion-c-col-left-region), and I have a question about this paragraph:

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> The point is that once you’ve made excuses for and come to the aid of a bad leader, it gets ever harder to say no to the next outrage. Republicans who defended Trump over the Muslim ban, his early attacks on the press, the initial evidence of collusion with Russia, have in effect burned their bridges. It would be deeply embarrassing to admit that the elitist liberals they mocked were right when they were wrong; also, ***nobody*** who doesn’t support Trump will ever trust their judgment or patriotism again.
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My question is at the end of the paragraph. Who exactly is the "nobody" the author refers to? I'm not really sure what "nobody who doesn't support Trump..."
even means. Does this mean Trump supporters or people that don't support Trump?
Is this correct grammar?