First, some clarifying statements. Homosexual tendencies are no crime because they are not a choice. To be tempted is not necessarily to sin. As long as one does everything in his power to avoid the occasion of sin and shun temptation, he commits no fault. Only when a person chooses to act upon his immoral tendencies does he give into temptation and commit sin.
Homosexual tendencies are usually the result of some form of abuse. An individual cannot choose whether or not he suffers abuse, so it remains true that homosexual tendencies are not a choice. If one was abused and as a result suffers from homosexual temptations, we must have nothing but compassion for their poor soul.
But the second one gives into homosexual temptations, a very grave sin is committed. To acquiesce to these immoral tendencies is a free decision, and it is a very terrible decision. The awful vice of homosexuality is one of the four sins that cry to heaven for vengeance, making it one of the worst possible atrocities of which mankind is capable.
And it is a choice.
God, in His infinite wisdom and justice, sends us no temptations which we cannot overcome. To send us a cross too heavy to bear would be unjust and thus impossible for even God. Though our trials may seem great, there is nothing we cannot overcome if we only ask for His help. This necessarily means that every rational person who commits these terribly immoral, homosexual acts has freely chosen to do so.
Woe be to these pitiable souls who call down upon themselves the vengeance of heaven!