It's fucked up even if it's neonazis (but I disagree with your usage of that term). It sets a precedent that you can willy nilly drop customers that might be relying on you.
Amazon did something similar to me a while back. I was livid.
It doesn't set the precedent (any private company can drop customers) and it wasn't "willy nilly" as you clearly acknowledge ("this was over nsfw content")
What's your stance on the gay wedding cake supreme court case btw?
When gab.com decided to use Stripe, they willingly agreed to abide by those terms.
It’s not like Whole Foods came out of left field, having no relationship to things at all, and all of a sudden said “you have to close your website.”