The Word says whaaaaaaat?
Jesus said if you look upon another woman with lust in your heart you've committed adultery.
The thoughts are sinful as well as the action. It's a further illustration as to why you can't be "good" enough to get into Heaven.
For this reason (for the objection ealgeone posts) I believe it is better to describe a person in such a state as “one with same sex attraction” rather than a “homosexual” or “homosexuality” in general.
The former term (same sex attraction) is one proposed by the founder of the apostolate “Courage” ( http://couragerc.org/courage/ ) to more accurately treat the condition for what it is, and the human being with it. Terms like “gay” or “lesbian” or even “homosexual” in general tend to label a person based on their sexual orientation or disordered state.
The founder of the apostolate argues that those terms actually dehumanize a person because they seek to create one’s identity based on a sexual preference. We are human beings, our dignity isn’t found in what type of sexual act we prefer. Our dignity is God given.
Regardless it’s correct to say someone with same sex attraction (or “homosexual tendencies” if one prefers) doesn’t sin by just having those attractions or tendencies any more than a “heterosexual person” does simply by having an attraction to the opposite sex. It’s only when either person acts on such desires (either by entertaining such notions in the mind or actually committing them) does sin occur.
Otherwise we ( men) who don’t have same sex attraction sin every time we notice a pretty woman walking down the street. An “attraction” isn’t a sin; it’s only a sin to then start fantasizing about others in a sexual way (and/or to act on such fantasies of course).