Eh, let's not make this an ageist or generational commentary - sure, an op can be younger than 20 thus making them a teenager, but I'd think that same scenario can easily play out with ops of any age.
Plain and simple, ops are frontline employees of the park, same as cashiers are at grocery stores - inherently these positions deal with the multitudes of personalities displayed by members of the public including several that appear to not have respect for other humans nor the environment they're in.
Compounding these exchanges are that theme park guests generally have an entitled mindset that they can do no wrong in the park, it's basically fairyland where nothing can hurt anyone and it's all for fun. While this (hopefully) usually doesn't have too many operational impacts to staff, it does make it all the more jarring if guests argue with staff over policy enforcement (granted, there's also cases of staff authority abuse too, but that's not the main focus here).
Add to that that company policies are usually in place to try to not upset guests (don't talk back to rude guests even if you feel they deserve it), these employees can be in a particular vulnerable position all while trying to do their job for relatively low pay.
While this doesn't excuse the ride crews of having inconsistent policy enforcement, hopefully it helps to continue to paint the picture that there may be other factors at play besides one op saying something different than another.