Why shouldnt he? Do you hate all you colleagues who quit? Lets be reasonable.
Football team is not the same thing as a firm. Although today the lines are blurred, but a firm doesn`t have millions of fans all around the world, aged from 5 to 105, who cry when the "firm" looses.
So if you think those two are the same, we don`t agree in the basics and discussion is probably pointless.
But even if Barca was a firm and season 17/18 was a project, everyone would be pissed if Neymar as an employee would leave like this right when the project is starting and people are counting on him. So yeah, I would hate a colleague like that. Fortunately, I had the luck not to work with people like that, so I don`t hate any of my former colleagues.
That being said, I didn`t mean that I`m dissapointed in Messi, but in general, because I wanted to see players telling him to fuck off because of the way he left. Not because he is leaving.