Ds1 (10) complained to me on Friday that his "friend" had been saying ds1 was gay because he plays with girls 
He was also telling everyone not to play with ds1 because he was gay.
So we had the chat about how friend was an idiot because a) there's nothing wrong with being gay and b) being gay was about boys fancying boys and girls fancying girls and nothing to do with who you play with.
My question is would you tell friend's mum what he'd been saying? I'm pretty sure she'd be horrified and hopefully would nip it in the bud.