Owning, opening and running a bar or a pub is not immoral at all. Why then are there all those pubs near Catholic churches throughout Europe?
The only thing is of course the abuse of alcohol. And there you have the duty as a barkeeper to say "no", when a customer drinks 'n drinks 'n drinks, and still wants to drive home afterwards.
It is not that serving alcohol is wrong. That's nonsense.
And college students "abusing" alcohol, well, that ain't your problem. They can buy it at a liquor store, and might use it for a nice party at their parents'. Then you could not open up an arms' store, because some crazy head would commit suicide with it. And a Catholic might as well close his household applications' store, because the knifes sold might be used by desperate housewives to cut their husband's throat.
During the work, one should warn customers if they are acting dangerously. But there is no obligation to "prevent" abuse when you sell legal products.