His treatment of Barkley has been nothing but fine as far as we know. He wanted him to sign, and he wanted him to play.
As for niasse. Niasse isn't good, guys. He was told that and put on the U 23's and told that they would try to get a deal for him to play elsewhere, which eventually they did.
Tell me why this is so "terrible"? It's football. It's professional football.
I'm not a koeman fan, but let's just stick to facts. He sucked as a manager, and helped screw up a major transfer window.