I think it depends on the person and the situation. Some people are not terribly good about confrontations, others are better. However, based on what the OP posted, it would seem to me that discussing this directly with the choir director would have been pointless. Clearly the man is unrepentant and is not going to stop.
If the OP were to approach him privately and say, “Since, by all appearances you appear to be living an active homosexual lifestyle, and homosexual activity is gravely sinful, you should not receive Holy Communion until you stop, repent and confess. In addition, you step down as choice director until such time as well.” Somehow, I don’t that would get anywhere. The choir director would dismiss it out of hand and probably accuse the OP of being a bigot rather than someone who is, in fact, the exact opposite.
On the other hand, hearing words like that from a priest actually carry weight. The priest can counsel the choir director and explain to him about the grave duty we take on when we get into line to recieve Holy Communion with the intent to recieve. As we walk to the front of the Church, we should all be doing an examination of conscience.
It is not about sin. It is about the appearance of grave sin in public being committed by a person serving a very visible and important role for the parish. It is about the grave sin of Scandal. If people actually did this more often, and if priests and bishops actually responded, perhaps the sex abuse scandal in the Church would not have been so bad and many of those victims would have retained their innocence.
Nope, the OP did the right thing. Though I can understand why you might be a bit uncomfortable. While it does seem a bit like tattling, you must also remember tha gossip, which is fed by scandal, is also a sin.