Just because something will end your career if overheard doesn't mean that it was something bad. Think of a lawyer on a long zoom call. What if they answer a client call and that conversation is pickup up by the zoom computer? Or what if someone in my office asks for login/account info and that conversation gets pickup by zoom? Or a system administrator sitting through a long zoom meeting about pension plans who accidentally has a side conversation about security issues on the production server. These are everyday acceptable office conversations that, if broadcast to zoom accidentally, can end a career far faster than looking unkempt on a webcam.

Sending a video feed that you don't want to send is not okay, even if it doesn't put you out of a job. The excessive severity is just exacerbating something that would be a problem anyway.

By which I assume you mean that the core problem is that they were casually denigrating the parents rather than trying to work with them?

Sometimes people vent. While I am not aware of that particular situation, bitching to your friends about some situation is different than live broadcast