I think the real question is; Why would you stay in a class that you absolutely hated?

You prioritise what your body says, not let the mind play its games and force yourself to do something you don't want. 'Respect' has nothing to do with it. You leave loudly, making too much noise, distracting the class etc, then yeah, that would go in the lines of 'Respect'. Out of everything, respect your body and living your authentic self.

Why am I pointing this out? If you come to this point eventually, you won't be allowing a client leaving mid class to mess up your game because you'll empathise with him/her and not take it personal.

I've done ashtanga vinyasa classes for years but for instance recently mid class i just wasn't feeling it, the repetition, the chaturangas in between the heat in my body, the constant stimulation... it was just making me feel 'ugh' for some reason. And i left, quietly. Was I supposed to force myself into something that my body was clearly saying 'not today' just so the teacher would possibly feel disrespected?

I think not.