Yeah, but in this case Stripe is one step removed morally as well. I don't see this as materially different from them being a payment processor for an online liquor store or a pyramid seller like LuLaRoe.

You could say that a payment processor should morally screen their clients in general, but that seems like a stronger and not-so-reasonable statement. They do prohibit certain kinds of businesses, but I think the bar for that is very high and likely related to chargeback concerns and such.