To me it looked more like IT lost his balance.
You have 6'8" 238lb Melo twisting the ball away from 5'9 185lb Thomas, with no space between them and the ref. IT losing his balance/stumbling is exactly what I'd expect to happen in that situation.
Kinda like with a jump shot, you have to give the shooter room to land, the ref should give a player room to stumble.
Granted, the shove and "hand grab" didn't look good on the replay, but it still would seem to me that was all more incidental contact from the ref being inches away while trying to wrestle the ball away from 2 players with a combined 63 pounds and 16 inches on you.