Okay, well, I am not a kink scenester as such, I'm more into fucking about at home, but my take:
You absolutely need to know your preferences, and be able to vocalise them. Yes, negotiation is a basic tenet
Thinking of Dude's reaction, though... Sometimes I get disproportionately righteous in response to someone nudging a precious thing that I feel is generally misunderstood. I wonder if it's the same here for Dude.
's dynamics definitely would mean that you could not hear boundaries directly from a sub. This challenges the social convention of strength / independence as being able to speak up for yourself. It can make people uncomfortable, and uncertain of a sub's agency.
While you were only expressing your comfort levels and possible boundaries, sometimes these boundaries themselves
can trigger a strong response from others, when the boundaries seem to be based on a misunderstanding. Does that make sense?
You're saying: this made me uncomfortable.
Dude may be reacting how he is because he thinks: what's making you uncomfortable about this? Do you misunderstand how these dynamics can work? Do you not get how she can consent to this, how she can be okay with the Dom speaking for her? i.e. is your discomfort because you misjudge the situation?
I'm not saying he's right, and obviously I have no idea why he's reacting the way he is. But... it could be that, maybe.