Some scary controlling people will tell you over and over how important consent is to them. They will tell you that they want to respect your boundaries, and that if anything makes you uncomfortable, they will stop. They will say this over and over, apparently sincerely.
Until you actually say no.
And then, suddenly, they create a reason that it wasn’t ok, after all, and that you’re going to do what they wanted anyway.
They will tell you that it *would* be ok to say no, and that of course they’d respect it, but you said it wrong. And that you have to understand that it hurts them when you say it that way. (And that you should make it better by doing what they wanted).
Or they will tell you that of course they don’t want to do anything that makes you uncomfortable, but you said yes before. And that this means that either it’s really ok with you, or that you don’t trust them anymore. And that you have to understand that it hurts when you withdraw trust like that (and that you should make it better by doing what they wanted.)
Or that they have a headache. Or that they just can’t deal with it right now. That maybe when they feel better or aren’t tired or grumpy or had a better day it will be ok to say no. (And that meanwhile, you should fix things by doing what they wanted).
Or that by saying no, you’re accusing them of being an awful person. And that they’d never do anything to hurt you, so why are you making accusations like that? (And, implicitly, that you should fix it by doing what they wanted.)
If this kind of thing happens every time you say no, things are really wrong.
No isn’t a theoretical construct. In mutually respectful relationships, people say no to each other often, and it’s not a big deal.