Both my older two babysat every weekend a few years ago - we're expats, & at the time were living in a compound full of young families.
Ds was nearly always snapped up first, & could've been booked 3 times over every weekend evening. He got very good at prioritising reliable payers, those good for substantial over time because they'd come home hours late & plastered, providers of pizza & a well stocked fridge, best Internet connections & cable subscriptions etc etc!
Dd1 was basically his understudy - still in demand but definitely second choice.
This was because ds is outgoing, funny & loves being the life & soul - happy to organise an hour of games & activities to wear random dc out before bed. He's currently planning a year abroad TEFLing - he's a natural with kids. Dd, OTOH, is sensible but quiet & shy. All our neighbours' dc clamoured to have ds babysit because he was such fun.
Had my ds been inclined to abuse the dc he babysat, he would have been in a perfect situation to do so by age 14 or so. Popular, known for clowning around, in demand with multiple families so any 'new' family could see that he had an established reputation...
I mean, my lad is lovely. I would trust him around any child I know, personally.
But here's the thing: I absolutely wouldn't judge any parent who didn't. He's a bloke & much more likely statistically, sadly, to be an abuser than say, his sister. & as above, IF he had happened to be that way inclined, he'd have had the perfect set up to be an extremely prolific abuser.
I don't think there's easy answers. It makes me sad that anyone would suspect my fabulous ds of nefarious intentions. But it would be entirely reasonable & proportionate to be wary of him/any other male in these circumstances, I think.