God is first and foremost about life. God IS life and the bias in all actions toward life and fruitfulness. A bias away from life and being anti-life is a trend line away from God and away from, ultimately, humanity as a whole. Therefore I have absolutely no problem with gays who have a genuine desire to have a child and provide that child with a loving, appropriate upbringing and family life.
Here is the theology. Catholics are entirely within their right to not want to endorse homosexuality, which is forbidden in the Bible, by refusing to allow children within their adoption agencies to be adopted by homosexuals. Gay prospective parents should have a generosity of heart and not try to force the Church to go against its legitimate doctrine through "equal rights" arguments. A gay who persecutes the Church regarding adoption rights is demonstrating a black mark against their parental heart and motivations.
Having said that, please note there is nothing in the Bible about homosexuals not being parents. Notice that the relevant passages forbid the homosexual acts, but certainly do not forbid a homosexual having a child. God always biases toward life. Honor thy father and thy mother is pertinent to both heterosexual AND homosexual parents, assuming they are good pious people who deserve to be honored. So Bible thumpers who state that God is against homosexuals being parents are flat wrong. In ancient times a man or woman who tended toward homosexuality would in all likelihood be ordered by the priest to go home and have relations with their straight spouse and have children anyway. This is because priests corrected perceive that the uniting bond among humanity must be a bias toward having children and toward life in all its fruitfulness.
I have a friend who is gay, and I've not had a chance to see him for a long time, too long in my opinion. While we've never discussed it I think he would be a wonderful father and would like to see him be a father one day. My preference would be for him to do it the natural way with a woman friend. But anyway, I think of him often and how happy he would be as a father.
I caution gays to not approach having children as though it's a technically complex project because as I pointed out about forcing adoption against a Church's legitimate beliefs, a complicated and cold test tube approach is a distancing from the naturalness of parenthood that is unfortunate. I'm most pleased when I read about a gay man, for example, having a baby with a woman friend of his because this is the closest to the natural way that I wish on all people, straight or gay, who pursue parenthood. You see, it's a testimony to the gay parent if he has a friend who would participate in parenthood with him, rather than be a monetary, political or scientific colleague in the generating of an offspring. See how cold those words are compared to "deciding to have a baby with a friend?" While infertility treatments are a blessing for many heterosexual couples who have problems conceiving, the laboratory should be avoided wherever possible when that is an option rather than the only solution. Again, I am counseling you all in my role as an "uber parent" and spiritual director that if you want to be a parent, walking as close to the path of natural parenthood is the way that is the most fulfilling and satisfying.
I hope this helps. I love gays who love life and children, with pure hearts and minds, and who wish to be parents. Please do not, however, ruin the parental experience by persecuting Catholic agencies who have enough problems without having to be martyred by gay politics. People and governments who persecute Catholic adoption agencies are showing a cold heart that is dubious both for parental goodness and in the eyes of God.
Do search out the most natural way of actually bearing a child wherever you can. A gay prospective parent who has a friend who would actually take the risk and make the commitment of bearing a natural child is a credit to pro life and good parenting.