The context, which is conveniently being ignored in most of the discussion, is that at this point you are already "fooling around", at which point it might actually be a fairly reasonable thing to do.
What you are describing is still sexual violence. Forcing someone into a form of contact they didn't consent to, even if there has been some other kind of intimate contact, is still sexual violence. A lot of sexual assaults occur in this way.
According to what I've gleaned from the folks against this book, you need explicit verbal consent before proceeding with that kiss even if the girl in question has been with you for several years. If not, you may possibly be unwittingly sexually assaulting her because she was too afraid to say no. Even if she kisses you back, she may be doing so out of fear.
So the key takeaway is; you can never be sure if you're raping someone or if you had implied verbal consent so if you don't have explicit verbal consent, stay the hell away from her.
And for you shy people who don't have the courage to ask your partners for verbal consent and never get asked; it's better to be celibate than a potential rapist.
If you are violating their boundaries, then yes. I don't know if you are aware of this, but people who have been assaulted may have a problem with people violating their physical space and you doing something that you consider harmless may actually be a big deal. The point is get consent and default to doing no harm, which is basic human decency.
The context, which is conveniently being ignored in most of the discussion, is that at this point you are already "fooling around", at which point it might actually be a fairly reasonable thing to do.
It also says "If she says no, stop immediately"