Here's what you asked.
I have kissed girls without prior, explicit permission. I did so expecting that they would not balk at it. I reckon that at some time, I was rebuffed, but I don't recall any such occurrences.
Franken kissed a girl without prior, explicit permission. It sounds like she was reluctant to rehearse the kiss at the time, suggesting that he shoulda knowed better.
But kissing a girl without explicit, prior permission is not by itself assault. It is how romances develop, even an hour or so after meeting a girl (who is at that point a nigh stranger). Outside of the university administrations, we don't expect verbal permission for every sexual advance we make. If rebuffed, of course, we stop, but at that point, we didn't commit assault.
There has to be something more to sexual assault than merely kissing a girl without asking permission, or even more than touching a girl's breast, butt or naughty bits without permission. I've done all those things, in appropriate contexts, been rebuffed many times for the escalation of some of those acts, but was not guilty of assault. Normal growed folk do indeed move forward sexually without asking permission and sometimes are told no, at which point such normal folk back off.
I'm willing to accept that Franken's kiss might have been a mild form of assault, but it would be nice to have a clear definition of sexual assault (in moral terms, preferably).