I Agree, sex does not matter when it comes to parenting and anybody can be a parent as long as the child is in a safe environment where they are able to grow up and be happy and feel loved.

Human beings have not biologically evolved to have sexual intercourse with humans of the same sex. If they were, there would be no point in two sexes, and humans would merely reproduce from themselves, with asexual reproduction. It is for this reason that the sexes have evolved to have differences. Men are made to be protective, women to be nurturing. I don't necessarily believe in homemaking, but I do believe that women are best for taking care of their own children in the beginning of the child's life.
But if you have two males parent a child, then the child will not have the nece…  Read moressary input from the mother, and if they have two mothers, they will not have the necessary input from the father.
I would argue that it is healthiest and best for two parents of the opposite sex, who are married and in a stable loving relationship. I don't believe homosexuality is natural, and I believe heterosexual couples should be the default.
However, I have the understanding that children who are raised by single parents can turn out alright, and therefore, why should it make a difference for there to be two of the same sex?
I would argue that with one parent, (let's say a single mother) has the motherly influence, and then there is no fatherly influence, rather anything else that may fill the gap, good or bad. The child may still find something to fill that gap, and prosper, or they may find something harmful.
Either way, that growth would be stilted if they have two mothers, where they are over exposed to femininity, and may have negative growth due to that.
A child needs the impact from both sexes to find their own personality and standing. Men and women are different, but I do not believe it is simply a matter being traditionally female or traditionally male.
There's a male, who had (effectively) no male in his life for fourteen years. He was damaged, emotional, suicidal until someone came along to give him more of a male role model.
He was given a positive male role model in his fifteenth year, and grew into a caring and righteous person with no hatred for any group of people, and a dislike for persecution or unfair stereotypes and beliefs. His hatred for both sexes and himself grew because of his parenting before that point however, and if he had had two female role models and no room for that male role model, he wouldn't have had that room for change, and likely would have grown up in hatred, resent and contempt.
I have nothing against homosexuality, so there you go. I don't certainly know two parents of the same sex would be destructive, but I have a suspicion too much of one influence would push someone too far in one direction.
Imagine, if you will, a child raised in a right-wing environment. Never given a left-wing influence, they will suffer ignorance and a type of grooming (either deliberate or incidental) and they may feel unsure of themself because they never had the option to question their nature with another. Or they may grow up with dangerous amounts of exposure to one ideology, or parents of only one sex.