you don't need to try so hard, just don't let him have weird ideas about gender and hope he befriends at least one girl. that'll be enough. all these idiots need is a female friend going "don't be an idiot that's not how things work".
Or a sister, or any woman who has the standing to tell you "your teeth are blotchy and your breath is bad, that's why people won't kiss you, go to the dentist"
It's easy to imagine them however you want. Truth is a lot of those incels probably come across as normal on the surface and have a normal life and are just depressed people looking for something to blame