I think 2 issues did for Matic. Firstly, he was on a final warning, Friend having made that clear to the captain, Maguire.
Secondly, although the shove by Matic was fairly mild for the 2nd YC, it did prevent a counter attack by City.
Even as a United supporter, I would have been surprised had he not been sent off.
That said, I wasn't overly impressed by Friend's performance either, and agree about the inconsistency.