Part of the manager's role is to get the best out of his players when things aren't going perfectly. Some players deserve a rollicking, others need an arm round. Fergie was a master at this. He knew which buttons to press with each player.
Surely, ETH's public ridiculing of Sancho was intended to get the best out of the player. It clearly failed spectacularly.
I think if the manager had his time again, he'd refrain from slating Sancho to the media.
Sancho's questionable attitude aside, ETH has failed to get the best out of his player on the training pitch or on the field. That can't be denied. He then loses his composure and slates his player publicly and the relationship is unsalvageable.
Horrendous man-management.