Well, let's see. Since marriage is between a man and a woman, and sex is something that is supposed to take place within the marriage bed, then I'd say that yes, homosexual acts are immoral.
Before you collect your cigar from LilLamb, let's look to the fact that the Bible nowhere defines marriage as "one man/one woman." The Patriarchs, Judges, and even Kings David and Solomon engaged in polygamy and concubinage without a word of moral condemnation. The account of Adam and Eve in Genesis describes what has always been a norm, but it does not prescribe that norm.
To move this discussion ahead a little...at the present time, the ELCA's policy is that its pastors will be celibate in singleness and faithful in marriage. Also, the ELCA does not recognize same-sex unions. So, gay clergy are to remain celibate. There have been some extraordinary ordinations of individuals living in committed same-sex relationships. (There have also been extraordinary ordinations of individuals who object to the Call to Common Mission agreement with the Episcopal Church). I don't approve of extraordinary ordinations because they violate the rule of good order.
In what I am about to say, I represent only myself. I am not in anyway representing the ELCA.
It is well-established that a certain, small percentage of human beings have an innate homosexual orientation. This is true in every culture and society. The cause or causes for same-sex attraction are not completely understood, but it seems clear that homosexuality is not a choice.
To say that all homosexual behavior is, in and of itself, immoral makes three options available to the homosexual minority. 1. try to live as a heterosexual person, 2. live in celibacy, 3. live in "unrepentant sin."
The first is to live a lie, which is not a healthy option.
The second, celibacy, is a heavy burden to place on homosexual individuals. Even the Apostle Paul, who wished that everyone could be celibate, recognized that this was not feasible for every person.
The third is to brand homosexuals with a label that they are bound to reject. It is asking them to repent of their very nature. It would be like asking you to repent of your heterosexuality.
In the light of today's best understanding of homosexuality (an understanding that was not available to the authors of Scripture) I think a better construction to place on the argument is, "How can homosexual persons ethically express their sexuality?" And the answer I come to is, "Just like heterosexual persons: by living in faithful, committed, covenanted, non-coercive relationships."
So, I am in favor of same-sex marriage as an ethical outlet for homosexuality. And, this being the case, I am also in favor of the ordination of homosexuals according to the same standard applied to heterosexuals: celibacy outside of marriage and fidelity within marriage.