It's referring to things like ridiculing or mocking minorities, immigrants, and disabled people. Which I think we can all agree are things that Trump did and have no place in a workplace like Grubhub, no?
But I think things get more complicated in the current environment where people who have voted for Trump have basically been labeled the same as him. It's apparently possible to have a "hateful attitude", or be racist, or whatever else, which can get you fired at GrubHub, by having voted for Trump.
But honestly, regardless of arguing intent or whatever, I think the crux of the argument boils down to this: If you had voted for Trump and worked at GrubHub, would you be comfortable going to the CEO and saying "I voted for Trump" without fearing for your job, after that email? I would imagine the number of people at the company who don't/didn't feel that is non-zero (purely based on a vote, not based on if anyone there is actually racist), and I view that as completely inappropriate.
The CEO never said Trump voters aren't welcome. That was the original comment that I disagreed with. It's factually incorrect to say that's what the CEO said.
"the new administration deserves our open minds and a chance to lead... never stop believing that the fight for what's right is worth it"
Obviously only excerpts from the full email[0], but seems to contradict what you just said pretty heavily. If I was someone who voted for Trump that worked at Grubhub, I know that I would have been afraid for my job after that email. Possibly even still would be, and might even consider moving jobs in order to not be afraid of that.
[0] The full original text of his email is at the bottom of this page: http://media.grubhub.com/media/press-releases/press-release-...