I was a foster child and I know that not every "straight" foster parent is appropriate for the child that is placed there. The state is so concerned with getting those parents that they are not looking at the best interest of the child or the qualifications that the parents possess.
The best interests of the child is the only thing that is important. The state should not be allowed to discriminate based on race, gender, age, religion, or sexual preference, among other things.
Let any parent that has the love for children and the means to provide for a child adopt. Having a homosexual parent will not make you homosexual so let's have at it!