Well that depends on how you define "good parent" doesn't it. Suppose Adam and Steve are living together with Adam's 13 year old biological son named Billy. Adam and Steve both love little Billy, who is now approaching adolescence and starting to wonder about girls and about what it means to be a man. Little Billy hears daddy getting corn-holed every night by Steve. "Ughhh ughhh ughhh....oh Steve, oh yes, put it in me.....". And you're going to sit here and try to tell me that this is not going to screw with little Billy's head? You're going to tell me that this is not going to confuse little Billy about what it means to be a man? About how he should interact with other men and with women?
I don't care if Adam and Steve say they love little Billy or not, it's child abuse. They are screwing with the kids head. John Lennon once said "all you need is love". Well you know what, John Lennon was full of crap. It takes more than love and good intentions. And just because you use the word "love" in a sentence, it doesn't mean that everything you do is therefor AOK. You want to play statistical games with me? Bring it on, pal. I'll show you a hell of a lot more statistics that show that children raised in "loving" gay home have about a zillion times more probability of long term mental problems. (Ya, ya, I know, you're going to tell me that "I know this guy who" was raise by gay parent and turned out to be a wonderful person, etc. etc., as if I were actualy going to believe you.)
Practicing gays raising children is child abuse, and this has been shown by study after study, covering thousands of children, across decades of time. Love is NOT "all you need" (Ya, ya, I know, this makes me an evil, bigoted, homophobic gay basher.)
Or suppose your mother is the heterosexual Susan Smith, and you are a toddler and your mother straps you and your brother into car seats and pushes the car into a murky lake. You and your brother cry as the water flows into the car and soon there is no more air to breath and only the murky water to fill your lungs?
Or suppose five siblings named Luke, Paul, John, Noah and Mary are drowned one by one by Andrea Yates, their mother in a bathtub?
So you see, simply because someone is a heterosexual does not make them a good parent and simply because someone is gay does not make them a bad parent.
And again, if you want to talk about statistics and facts, I can show you that heterosexuals kill their babies in far larger rates than gays.