So...if you act inviting early in the evening, you're asking for anything, and I mean anything, that may happen thereafter. You're the one choosing to send signals; there's an obvious conclusion. When you actually get near the ftb and find that there's a checkpoint where you cannot say no, it's entirely your fault for putting yourself in that position and you've got no one to blame but yourself.
That reasoning is unacceptable in real life and I think it excuses nothing in game. "No" should always, always, always, always, always be a permitted answer.
Not to mention this situation can occur without having chosen any
[Flirt] options, as demonstrated in Bright's linked thread (which is broken, by the way).