It's nearly impossibly to date someone and not sexually harass them in some way

You have horrible relationships if you think this is even remotely true.

It's doubly hard to break up with someone and not sexually harass them in some way.

And even worse break ups.

That or you don't know what sexual harassment is which I'm thinking is far more likely.

it's almost impossible to draw the line between sexual harassment and break-up banter.

No its not.