He's probably caused less damage than most of those criticising him.
We have no idea how he's gone about his self rescue practice, and generally this practice is no bad thing. Prussiking up a rope isn't necessarily any worse to the rock than top-roping. I'm sure he did it in a very clean manner. Benefit of the doubt given.
I'd probably give it one more hit in better weather. Sorry to hear about your unpleasant experience.
The people at high rocks have a long and checkered history with climbers, there is no feeling lost between the two parties. Other climbers have aggravated the owners in the past by trespassing and damagine fences. They are of course very snotty towards climbers, and don't really want you there. They are more of a functions place and climbers are just about barely tolerated. However, there's not a whole lot of choice, and plenty of climbers can swallow it because of the lack outdoor climbing in the South East. Basically, don't do anything to jeopardise access. Go to one of the other crags in the area that aren't so hostile and go north at weekends.
It might be shit and a rip off, you may also get snotty horrible service from the staff for reasons unbeknownst to you, but they kind of have the luxury of demand. Access is delicate, and it's closing would be a massive hit to the climbable outdoor rock in the South East, so that's why people are very defensive of the place.
Post edited at 17:41