I am I think agnostic but I thought a big part of those that follow Jesus is that they accept they are flawed people and do things they should not do.
I have been around a ton of Christians and almost all of them think they do and have done things they should not do because of the weakness of being a human.
He could easily be one.
The thing about Christianity is that it's quite varied. Some forms of Christianity (denominations/sects, if you will) are are simpler while others are more complex. Some emphasize the love of Christ while others tend to emphasize God's judgment.
Within Christianity, there are even conservative and liberal forms of the faith. Conservative churches tend to interpret the Bible more literally, while liberal churches are more willing to interpret at least some of the Bible allegorically and also take into account the time and place from which certain books sprang when forming their understanding. Regarding homosexuality in particular, some churches go so far as to argue that the Bible's actual message on it is quite misunderstood and that the practice is not really condemned at all.
Catholicism is a very complex version of Christianity, quite different really from the much simpler Protestant denominations. It's also a very legalistic (rule-based) form of the faith. Catholicism goes so far as to have two different kinds of sin: venial sin and mortal sin. Venial sins are those sort of lightweight sins that we all find ourselves committing: little white lies, calling someone an asshole for no good reason, brushing someone in need off when you could've helped them. Mortal sins, however, are more serious and the Catholic Church teaches that if you die in a state of mortal sin then you go to hell.
For a sin to be mortal, it must meet three conditions:
1. It must be grave matter.
2. It must be done with full knowledge.
3. It must be done with deliberate consent of the will.
Homosexuality is grave matter and Milo is committing the act with full knowledge that it's a sin. Where it could be argued that he fails to meet the standard of committing mortal sin is the area of "deliberate consent" (since as a few others have mentioned he seems to not necessarily WANT to be gay). But this just gives you an idea about how much stranger, and how much more serious it seems, for a Catholic to be gay than for, say, a left-leaning Episcopal who has a pretty different idea about God and what God wants.
