I would agree it is an intrusion if it's made clear that it is unwanted

That is minimal acceptable behaviour..

You need to need to use your judgement.

I mean, until you are given an indication that it is unwanted, are you (or more accurately, am I, a male) supposed to expect any advances to be unwanted?

I am a male. I want to put my penis in your orifice. Is there ever a moment in your life when its just not appropriate for me to ask you? Are there moments in your life where it is okay for me to ask you? If 30 guys asked you in one day, would you find that annoying?

Use your empathy dude.