Deskdairy - // But why is it so wrong to hold the opinion that the best environment for a child is a mother and father? //
It's not wrong to hold any opinion, but in my view, the popular belief that a man and a woman are the best parental combination for a child cannot be put forward as a uniform template for everyone.
Prior to modern times, this was the accepted norm, from a time when no-one actually questioned the idea - but in these days, when same-sex relationships are far more open and accepted than they ever were previously, then same-sex relationships with children become far more prevalent, and the old order is challenged.
From personal experience, the family I grew up in, with the 'normal' set-up of a mother and father was a horrible dysfunctional environment from which I was delighted to be liberated.
My view therefore is that a mother and father for a child is the norm, but it not the best simply because it is the norm.