If he re contextualised it to show his growth rather than about "haters" he would've been fine.
Not speaking about Tyrone May in particular - but a lot of athletes use the "haters" as motivation. It's what gives them their edge. And without it, they can't perform. Especially those that come from lower socio-economic areas. We need our players to have that kind of edge or chip on their shoulder.
And when you've bottled that up for 2 years, and finally reached the top of the mountain, it's all gonna come out somehow.
Lot's of sport psychology studies into this kind of stuff, and anectodally you can see it in the fact that only 1 team has gone back to back in the NRL in the last ~30 years.
We can probably see this exact thing playing out with someone like Jarome Luai right now. Kid from the hood, never meant to be anything. Suddenly he's an Origin star, and won a premiership. Now he think's he's got it, and performing like shit. Probably the best thing for us/Jarome right now would be for him to mouth off to the wrong guy, and get an absolute flogging - and he can channel that feeling into his football.
On Tyrone May specifically, regardless of his intentions, perception is reality, and he missed the mark with his IG post. You're exactly right in that a message about growth would have gone down a treat, especially if he rocked a nice turtle neck/sweater as well!
I personally think he'd still make a positive contribution to our team on the footy field - but understand if our management and sponsors don't want that kind of baggage. Having said that, the black listing of him by our club following his release was/is shit, and completely undermines our club values.