Hey so um.... remember this line from the Abbott crossover
I'm sure some people thought (me included) that this was just a reference to Dennis' sex tapes, that the only reason he knows about filming consent is because he doesn't want to get in legal trouble while he does his... sex escapades.
But now that we have the context of this latest episode, I think it has more to do with his time on Family Fight.
The reason why Dennis knows about consent laws is because he probably tried to get the network to not air this episode. He read that contract over and over again and found out that his meltdown would get aired no matter what. He doesn't have any rights to it now, he sold them away when he signed onto the show. So now he's afraid of being filmed without his consent, because he's afraid of humiliating himself again. That's why he was so weird in the Abbott crossover.