Your entire struggle to understand this issue could best be summarized, in resolution, as this: homosexuality is the sin that requires being rejected as the sin it is inorder for anyone to be qualified to represent Christ within the Church, as Priests are relied upon to do.
While someone continuing to claim to be a homosexual while, in your suggestion, being celibate, not engaging in sexual acts, they continue to embrace and affirm the presence of homosexuality. And, celibacy is more than merely refraining from overt physical acts.
A man fantasizing about, desiring for, romanticizing over and for some, seeking overt sexual contact with another man, whether a Priest or any other vocation, is a homosexual. The issue is homosexuality as a "disordered state" so well described by Pope Benedict, and that also and again, homosexuality is deemed "an abomination" to God.
The only time in the whole extent of scripture wherein God uses that degree of harsh condemnation for any human act is about homosexuality. He doesn't say "it's pleasing as long as a homosexual is celibate," He says that homosexuality is an abomination in His sight, in His eyes, and that means that within the perception of God about humanity, homosexuality is the one and one only thing that is abominable to God. Pretty harsh language, and pretty clear.
The example of alcoholism is relatively but not completely accurate but generally speaking, the issue is that to someone who is alcoholic, they remain that way whether or not they drink alcohol or not...they're still an alcoholic. And, to someone who self identifies as and with homosexuality, they remain doing so despite religious vows. And that leads the Church to conclude that the requirements for the Priesthood exclude homosexuals because homosexuals represent a state of human existence that is not qualified for the Priesthood.
All the issues as to homosexuals in the Priesthood engaging in overt sexual acts in defiance of their vows and that includes pedophilic acts, those are dreadful amplifications of the same disordered state that already exists, yes, but the decisional issue about the state of homosexuality, to my read and reason, rests in the fact that the state of homosexuality represents a disordered state in and of itself, and scripturally is severely judged by God to be abominable...thus, an aspect about a person that is not fitting for the Priesthood.
I wrote this earlier and I'll write it again here because what I find most telling is that homosexuals currently in the Priesthood opt to threaten to leave the Church and abandon their vows in light of this instruction from Pope Benedict but they don't consider abanding the sin itself of homosexuality, in effect, refuse to recognize God's very statement about it, and/or if recognizing, are rejecting God's terms.
Interesting choice.
Interesting choice.
Interesting, indeed.
Oh, if only they would!