Their work, their infrastructure, their call. And a good one as well. Don't provide nazis with anything.
Would you support the same thing done by, say, Christian bakers not providing a customer for religious-ideological reason?
I didn't follow the case and I'm only tangentially aware of it, I don't know who said what to whom and to how any of it is handled. I can't say with 100% certainty knowing the full explanation of the case that I would side with either the Christian bakers or the customer.
However though, it should be within a business owners right to deny someone access to a paid service or good on essentially any grounds.