It’s a pretty heroic assumption that the post was as simple as a ‘lack of remorse’. It might well be part of it, but is he not showing remorse for playing footy as a kid or winning the premiership now.
But even if it was as simple as that, a lack of remorse isn’t a sackable offence. Whether we like it or not, May has a right to post his feelings on Instagram. If it was directed at certain individuals or parts of society, then he actually did it in quite a classy way. He might not have thought about the uproar it was going to cause, or maybe he did and that was the point of the post; but not a sackable offence.