Is it time to start calling out bad cyclists?

He was in the middle of the road cycling up from the lights by the hospital and I was behind him in the cycle lane. He was going quite slow so I was catching him up on the inside.

This does sound a lot like undertaking, if you overtook you would have been on the right of him, if you were a safer distance behind him whilst of the left then his wobbling back to the left wouldn't have led to you two getting so close.