If you run a shop, you can't decline service to democrats, even if disagree with them. You can't discriminate, that's the law. I don't see how is it radically different from running a hosting company.
It is in California (which, obviously, is located in the US).
Presumably landlords in DC can still kick people out for wearing an Obama / Trump shirt. (That’s supporting a candidate, not a party.)
I’d be curious to see court precedents on this.