Why though? There's nothing to disagree with what he said. Both the players and the coach are responsible for the performances a team puts in.
There are no two ways to look at it; the coach is the one pulling the strings, he's the one in command. He's the one to punish or fire them up when needed. He's also the one who picks who will be in the first team.
It's his job to make sure everybody is in a good state of mind when on the pitch. He can't, of course, control what happens in the outside world, but again it's his and the players' responsability to, in a professional manner, perform as they're expect to.
You can't blame the players alone. You take away the tactical aspects of being a coach and what's left? Leadership, motivation, and sometimes bond. I've seen many and I mean many Brazilian coaches Through out the years who were truly tactically inept but were fantastic motivators and leaders. Sometimes that's all that's needed when you already got intelligent experienced players.
So Yes, players having a poor mentality is most definitely his fault as well.