another time it was a bunch of school kids in class screwing around
Yup. And everyone felt like idiots for having made them feel unwelcome afterwards.
Err on the side of kindness.
For anyone concerned about copyright infringements. It is fair use. It is fair use in the exact way fair use is intended to be used. PSC is not a 'publisher'. If a person takes a work largely dependent on that original work and decides to publish it and/or profit from it by branding, then they are liable to the original creator.
In any case, not the concern of PSC.