Speaking as someone who was manipulated and coerced into giving oral sex despite my clear and emphatic, repeated "no," I am really upset at the people going "she went down on him, therefore she consented."
Men who do this are manipulators, plain and simple. They know damn well you don't want to. They don't care. They know all the buttons to push to make you do what they want you to do, and what you want doesn't matter. It is actively, intentionally predatory.
The guys who act like if you didn't get up and walk away it was your fault are goddamn liars. They know what it feels like to be in a situation where you don't feel like you have a choice. Where social and emotional pressure are brought to bear to force them to do something +