It depends on what people think in general about: Why homosexuals are homosexuals? If the majority think it is because of a genetic reason, then the adoption idea would be more acceptable. But in case they think it is not genetic but more about how childern are raised, it will be more difficult to accept.
That depends. Many religious people ( I am not religious myself, and I don't wish to offend anyone who is) believe that homosexuals are born gay but that it's still "'wrong." That's why they try to "reform" them. It's seen as a "'defect" that can be changed. In the absence of that, many expect gays to remain celibate for life.
So even the "they are born that way" doesn't work with some people.
Personally I think anyone who does not observe that there is at least some genetic component to homosexuality is DENYING REALITY. I don't want to stereotype completely- but there are many people who are obviously gay and they do not purposely go around advertising it. Sure this is not true for all, but many people are obviously gay and it is given away by innate not chosen characteristics.
To me I think most people are born that way or at least leaning strongly to a certain orientation. However, I do not really care either way- as I don't find anything wrong with it. If it is a choice, people choosing that doesn't bother me either ( some people probably are born bisexual as well or however you want to describe it and have a little choice at least).
FWIW, the churches I am comfortable with- if they oppose homosexuality as one of the sins then they treat it like any other sin. No more no less. Though personally I find nothing wrong with homosexuality- at least this view seems consistent to me. What I find particularly distasteful is those who have some kind of OBSESSION with homosexuality as some grave sin and danger to society above every other issue. Some characters like this would prefer that children are abused , molested, and murdered rather than have them "exposed" to a homosexual parent. Among other things.
A lot of other things are considered sins and many religions consider ALL people to be "sinners" so I guess NO ONE should be allowed to adopt.