For something perhaps a bit more digestible: "I believe no one under the age of 18 should become gay. I have a kid that pretends he's gay, but I'm nowhere near considering that as real. He's just pretending! No way is my kid going to be a gay at this age; that's ridiculous! P.S. It totally makes sense for my Avatar to be something self-describing as an LGBT ally!"
Yes, I'm sure his possible daughter isn't negatively affected at all by her dad telling her she's "Pretending" and that it's "Ridiculous". But hey, he's a self-professed Ally, so that's all fine, right? She might, if she can muster the courage for it, have a relatively pain-free early experience, but it's also possible that she internalizes that attitude. Note that even when she'd be older it's just that the dad "might consider it". Because hey, it's not like it'd be something she already is, it's just something someone decides to do to themselves. Y'know, like your kid getting a piercing.
But again, he doesn't outright oppose basic human decency, provided he gets seven years to consider if it might be okay, so being offensive is totally fine.
P.S. No, it doesn't get me to "Hate people". Like I said, it's not my image, but people are very eager to get the social cred for "progressiveness". That doesn't automatically make it so.