Pony tailed man (Rant alert)

You must have one in your office or in  the area or as a minimum seen them in the street. Bald middle aged men with a smallish pony tail at the back. We have one in our gym. He is German, losing is hair but with a small pony tail at he back (similar to the picture).
He is a bloody pest. He spends 95% of the time talking to people about how wrong they are doing the exercise but never doing any himself.
Other times he stands looking at people doing their exercise and then shakes his head and moves on. He hopes they will say what? and then he can tell them.
He never ever does this to the real weight lifters and muscle men in the gym who just totally ignore him. which is the best thing too do.
The plonker!