The ref didn't send him off for denying a clear goalscoring opportunity. That has nothing to do with it. Terry tried to slice him down with his foot; which Jo evaded. Then Terry put his arm around Jo's waist and pulled him down. No attempt to play the ball at all. Just another instance of Terry (And Chelsea in general) thinking they can get away with anything.
But a good example of referee's earning respect - David Moyes is going to get a touchline ban for his reaction. But Howard Webb has suggested it should be as little as possible because he accepted that he made a mistake in not giving Everton a penalty at some stage in the match.