This one's fairly clear-cut.
The Talmud says it's prohibited to sell frankincense in small, retail amounts to pagans that they will use in their pagan worship. However you can sell it in bulk as wholesale, and what the retailer does with it is not your concern. I may not enable a non-Jew to worship idols, but I may enable the enabler. (That's indirect enough.)
It then tells the story of a rabbi who sold firewood to a pagan temple, and was challenged by a colleague about this. He replied that most firewood consumed by that temple would simply be used to heat the building, not in any pagan ritual.
The Shulchan Aruch quotes this law, and then adds -- "and therefore, don't sell water to a church that will use it for baptisms." We see that generally, the rule of "don't sell pagan supplies" was applied to churches as well (well at least Orthodox and Catholic churches -- Protestants is a different question entirely). (Though there may have been leniencies about this as well.)
However, it's then observed that there is a very strong opinion that the only problem is enabling when I am the only supplier around. If instead of buying from me, the pagan could buy from some other frankincense supplier, then I'm not truly "enabling", and it would be permissible.
In todays' markets, it's virtually unheard-of that my refusal to sell a product will actually prevent them from acquiring it from someone else. Hence selling it would be "facilitating", but not "enabling." Most rabbis conclude that "facilitating" is not ideal, but it's allowable.
Thus -- as long as there's some other wine they could buy, I'm not prohibited from selling it to them.
(I once witnessed a Catholic woman enter a candy store and say she needed any sort of candy so long as it was red, it was "for the saints." I asked a rabbi about this -- he said firstly, we don't necessarily know what "for the saints" means; and secondly, we can rely on the opinion that it's allowable if there's some other place in town to buy red candy.)