I think the league might be worried it's more predatory than anything.
The way I see it is that there wasn't an easy play to make at that juncture. It was a close puck race with Buff moving East -west towards the boards to get to the puck and Gallager moving north south towards our net to get the puck.
If Buff is late Gallager is in for a break away.
If Buff just gets the puck and tries to pivot around Gallager (avoiding contact) he runs the risk of having Gallager knock the puck off his stick and going in on a breakaway.
He elected to play the puck and simultaneously negate the threat of Gallager having a chance of getting the puck. It imo was the least risky play for Buff to make in the situation.
With regards to the hit itself, it didn't look that bad to me but obviously the league has some issues with it. If he is suspended I look forward to seeing what it was that they saw.