Ed said it[1] better than I could, so I'll quote him:
This is a long way of saying to the people who support Trump (and therefore would never read this) that "Let's agree to disagree and keep being friends" is a poor strategy this year. However you've managed to rationalize it in your head, supporting someone so openly and enthusiastically racist, xenophobic, and flat-out mean says a lot about you.
We are long, long past the point of pretending that support for Trump, let alone actual material and financial backing, is a matter of mere "politics" (as if that in itself is some harmless affectation).
Peter Thiel took one look at the failing campaign of a vociferous racist, mysogynist, authoritarian, anti-democratic fascist, and said "I'll give over a million dollars to him."
How can we trust the business and social acumen of a person who makes that kind of decision? Who faced with a losing candidate will throw good money after bad. Who faced with a business landscape that is crawling, desperately, into finally opening its doors to women and minorities, happily funds a man who says you can "grab [women] by the pussy," that "we ought to build a wall" to keep out Hispanics, and openly campaigns for barring Muslims from the country (who, I might point out, are statistically as likely to be South Asian as Arabic, a demographic hardly unrepresented in tech).
You wouldn't find it so bizarre that a man who has swastikas tattooed on his face had trouble finding a job, why do we find it so bizarre that a man who has done far more actual material harm might not be appealing to a business partner?
[1] http://www.ginandtacos.com/2016/10/17/the-difference-between...