Re: it is only fair that we fine some of theirs back!
"the UK fined Facebook half a mil (how they must be laughing now)"
That was the maximum the ICO were allowed to fine Facebook under the regulations at the time. Now with the GDPR it's a percentage of the offending company's turnover. 5% if my memory serves me correctly.
So no, it wasn't because the ICO went easy on FB, they had no other choice.