For me it's not about hurt feelings or anything like that. Having a coach blow up at me would be distracting, and I'd be thinking about it for the rest of the game. It would not be good for my performance at all. Maybe I'm soft that way, but that's just how it is. If Witts isn't like me, then maybe the spray was a good thing for him. Otherwise it was a bad move on Buckley's part.
For example, do you reckon Jack Watts would respond to a physical kick in the bum like that? Hell no. He'd play like shite and might even want out of the club. Jake King probably would love it though. There are some people you need to talk to, and some people you need to bake.
It's not about "deserving" a spray. It's about responding to a spray. The purpose of a spray (or anything a coach does) should be to get his players to play the way he wants them to play. Spraying someone because you're [censored] off does nothing, and makes you look like a dill.