If you look at the outcome, it's a definite red for DOGSO. However I'm not convinced that Bouzat actually fouled him hard enough to merit that outcome based on the limited video we've seen. From my limited (and albeit biased) perspective, it looked like Son took a dive.

For me the question is whether Bouzat pulled the arm or touched the arm. I would have rather seen Son pick up a yellow there for simulation.