I'm like you with many friends and family scattered around the globe.
I still don't agree he is any more unreasonable than you are.
You have different opinions, both with good reasons although I think you're somewhat naive about just how easy it is to hack online accounts.
Near this in mind - many of the people who develop/own these products DON'T allow their own children to have accounts and don't post their pics online.
Personally I've posted pics but never anything where dd was in any state of undress, nor anything that identified eg what school she went to. And I taught/advised her to do same when she started to have her own accounts, advice which she still follows now at 18. She doesn't have any overly identifying info on her profile like dob, where she works etc that's just sensible precautions.
I've also always had the highest possible security settings and regularly check them (because updates and "improvements" can knock these off without you knowing)
Your dh's stance may be unusual but he's not necessarily wrong.
I certainly NEVER allowed school to use pics of dd, they can't be trusted to keep them secure and it immediately identifies which school they're at (often with helpful full address, maps etc) so on that I actually think you're being very unreasonable