A lot of Trump's support comes from the alt-right.

No it doesn't. I'm willing to bet 5% of Trump voters identify alt-right. They don't even have any political values, conservative or not. It's just a weird Internet cultish movement. Many of them aren't even American.

I can't really think of anyone that would be as stupid and awful as Trump, which lends itself to my view that as bad as the regressive left is, the alt right is so much worse .

Have you bought into how Hillary's campaign branded Trump as the alt right leader? The altright is not an organized political party with party principles. They're just a bunch of reddit/4chan trolls having fun. I don't understand you point here. Progressivism isn't so band when compared to a fringe online political movement?

Could someone that believes in open borders win the left over? Someone that believes all of America is a "safe space?" I doubt such a person would even make it to the primaries, let alone compete there. But then, I thought the same of Trump...