Demens is fine here, I think. Mesh is tough on LBs in zone. Here he lets the receiver outside of him but he has to expect Avery will be there. He also knocks down the other guy running a drag, which is a bonus.While I agree that Demens wasn't the main culprit on the touchdown, he was largely responsible for the blown coverage that led to the touchdown.
What's especially disappointing is that, as you can see in the final screen, Craig Roh had gotten to Stanzi on the pass rush. Had Demens even feigned coverage here, it would've made Stanzi hold onto the ball longer and either make a poor throw or eat the sack.
I'm going to go back and watch the game to see how well Demens did overall. I'm fairly certain he did better than Ezeh (something that the Michigan blogosphere is mostly in agreement about), but I think MGoBlog's UFR probably overlooked a few plays like this out of sheer excitement and hope.