At the risk of sounding the non-PC one here, I still believe in the idea of the nuclear family. (two parents of opposite sex, plus children.)
I feel this is the ideal situation, but can accept that when a persons sexual orientation changes mid-life, they may already have children, and the best thing for those children may be to continue with a particular one of the parents. If this parent is then involved in a long term same sex relationship, then I would still support the parent's right to the upbringing, and the love and support of the child.
However, once one has made a choice about ones sexual orientation, which puts one into a relationship in which the 'couple' could not produce a natural family, I feel that to expect to be allowed to adopt, "As A Right", is unreasonable.

Where there are too many children seeking too few adoption places, then I can accept that adoption by 'same-sex' couples is a valid option.

So despite my initial comments, my only objection is to any attempt to make it a legal Right, as opposed to an option for consideration.