In equality and a fair world it should work regardless of a homogeneous or heterogeneous relationship. However this is not an equal and fair world, this is real life. Theres still blantant racism and discrimination in it.
For that reason, IMHO it is unfair and irresponsible for a same sex couple to adopt or rear a child, and to let the child grow up in amidst of that discrimination. There's no way he/she will be unaffected by that, especially by his/her peers. Kids are the worst to each other when they are young.
That being said, its only my opinion. In the end do what you want anyhow.. its really none of my, or anyone else's business what the fawk you do. Its your life, lead it how you want to.