That wasn't a red. It certainly wasn't as bad as Pogba's on Otamendi anyway. Young on the other hand should have been sent off twice.
1st pen (in the 1st half) was absolutely nothing (arm didn't move, and it was flat on the ground - ball to hand)
2nd half - more 50/50 (impossible for either ref or linos to tell whether he got the ball or not) , but Sane should have already been off anyway by that point for MUCH more obvious yellows