I don't think that it is strictly limited to OAT per se. For some inexplicable reason this industry seems to attract people that can't help themselves than treat newbies with disdain even though it is these very students that enable them to earn a buck.
In my time I have met ex RAF navigators with chips on their shoulders and a deepset hatred of pilots in addition to ones that would give of their time without question to get you through the ATPL's. I have met 10,000 hour C-152 rated CFI's who think that the be all and end all of aviation is their crappy flying school operating out of a portacabin and will tell anyone who can be bothered listening how they chose not to go commercial even though they had airlies beating down their door but decided to concentrate on training. Yeah right! I have come across prats that insist on doing their PPL's in a captains uniform complete with epaulettes and the nice shiny black leather flight case. Best of all though is the brand spanking new PPL holder that started to offer flying tips to newbies and regaled stories of how it was all just so simple for him.