That something is the subject of heated debate is not in any way indicative of its virtue. Every single thing in human history for which there have been disparate opinions has been the subject of hot discussion. At some point, it becomes clear which side is wrong.
There is a number of critique of methodologies of the studies on which American Psychology Association based its famous statement about gay parenting being as "equally supportive" as hetero parenting (including convenient samples, short term outcomes, inadequate comparison groups). The majority of the study was for lesbian couples. Regnerus study in 2012 reports statistically significant worse outcome for adults who had unstable (hetero<->homo) carers/parents in comparison to adults who had only hetero carers/parents (this is already after his correction http://thinkprogress.org/lgbt/2012/10/30/1110591/regnerus-admits-gay-parenting
Many scentists confirm the necessity of further research, especially for long term effects of having LGBT parents.
Having said that I must admit that I am astonished after exploring this subject in the internet. I didn't expect such an amount of research results described on reputable portals, reporting no evidence of negative effects of having LGBT parents whatsoever.. This is indirectly contradictory to what I read in literature around 20 years ago. I was reading a lot about the subject of family, but from a different perspective. There wasn't anything about gay parenting, but rather about the stability of the family in general and how important it is that children have both parents because each parent plays an important role (father different than mother, appart from the fact that 2 is better than 1). (and the literature was not religious, btw) I wonder how it is possible that after 20 years the distinct roles of parents as mother and father are no longer claimed to be so important. I was expecting to have numerous arguments against LGBT parenting, but it's actually difficult to find any. This put it under question how can you take it all seriously (now, then or both).
One possibility is that it's just the fact - nothing wrong with LGBT parents.
Another posibility is that it's just a strong lobby for new "political correctness", because LGBT family is better than no family.
Yet another possibility is that science and research is sometimes broken ( http://lesswrong.com/lw/ajj/how_to_fix_science/
) and a dose of optimism and trust is needed to choose the side.