Easyjet have nothing whatsoever to do with the check-in service provided at the airports featured on the TV programme. All of this work (and ground handling of the a/c out on the ramp) is contracted out to a variety of companies who 'specialise' (used in the loosest possible terms) in these activities.
Given that these companies pay minimum wage and generally treat their employees in an increasingly shoddy manner, it is hardly surprising that some of the dimwit/rude/aggressive (delete as appropriate) passengers often end up on the receiving end of less than sparkling service.
Easyjet frankly couldn't give a monkeys as long as the money keps rolling in, and neither could the various service providers' managers so long as they continue to con the airline into believing everything in the garden is rosy and pocket their nice fat performance bonuses.