K I'll be that guy.
The block is borderline dirty after initial contact. But it's also really hard to tell what's going on.
Either Brown makes contact initially, disengages and then lunges at the side of Miller's knee...
Or Brown never disengages, and in fact drags Miller down awkwardly.
Initial contact is completely fine-- maybe that's what you guys are judging. But after initial contact, Brown is spun out of Miller's path to the ball carrier and the only way he can realistically slow Miller is to drag him down or do something weird like rolling up in the side of his leg.