If you feel a girl wincing in pain or squirming to get away and she seems frightened, YOU HAVE TO STOP. It's what good partners do. Not stopping is what a rapist does.
I'm not sure why I feel like talking about this now, but I do. I haven't really shared this with anyone who doesn't live in China, so this is a first...
What you just said is a cultural phenomenon. It is limited. I'm not sure how many cultures it is true in, but I do know there are cultures where it is not true. One of those is China.
(this is a bit explicit, so ignore it if you want...)
The first girlfriend I had in China wanted to take things a bit slow, which I was totally fine with. On the sixth or seventh date she came to my place and we got in bed. After a while I went to take off her shirt and she said "no". Quietly, and without much effort, but she said it. So I stopped and we took a breather. A minute later she got back on me and we started making out. When I eventually went for her shirt again, she said "no" and I stopped again - as would any self-respecting Western male. Again she was unhappy and I couldn't figure out what I'd done wrong. This happened in a slightly different fashion over the next three dates. On the last one I had gotten her shirt off and was trying to go for more when she pushed my hands away and said "no" again.
The morning after the last of those dates I was talking to her and she was obviously unhappy. I honestly believed it was because I had tried to go to far and she was offended. I asked her if that was the case and she looked at me like I was crazy. "Tyler, we've been going out more than a month and we haven't done
anything! Why don't you take control? Do you not want me?" I was blown away. I was totally suspecting the opposite, and yet she was unhappy that I hadn't gone further! I told her I stopped because she said "no" and pushed my hands away. (In retrospect, I should have just said 'sorry, don't worry, we'll fuck tonight' and stopped thinking about it.) She shook her head in disgust at me and stormed off.
So a night or two later we get back into bed and I get the shirt off, the pants off, etc. all with some minor resistance from her. I figure she's made it clear that she wants more, so the minor resistance must be meaningless; if she starts putting up any bigger of a fight I'll stop.
Finally we get to the big show. Just as I entered she grimaced in pain. I asked her if it hurt and she said "ohhh, yes!!" So I pulled out, tried a different angle, and gave it my best shot again. Each time I tried to go in it looked like I'd just taken her virginity (I hadn't), and she looked horribly uncomfortable. I asked her if she wanted to stop and she said yes, it's too painful. So I stopped. This was my first girlfriend in China and I really didn't want to mess things up, so I was totally okay with all this. She, on the other hand, continued to look horribly pissed off. I'm not sure what caused me to get over my fear of being too aggressive, but I eventually just pushed her down, got on top, got inside and started to go to town. After about a minute it was pretty clear that she was enjoying herself.
Afterward we lay together totally content. But every time we had sex it was the same song and dance. She would protest at the removal of every piece of clothing, say I was too big and that it hurt too much, scream like I was beating her in the face and nearly cry. And she wanted me to hold her down, force it on her, etc.
This is not unique to this girl. Since that time I've had enough experience in China to know it's quite common. Even a girl you sleep with regularly - girlfriend or otherwise - will often protest every step of the way, but be disappointed and disgusted in you if her protests lead to you stopping.
The natural question is "well then how do you know when it really is rape???? If every girl is going to pretend like she doesn't want it, how do you know when she really doesn't want it?" There are a bunch of answers to this one in China. The clearest one is that no Chinese girl is going to sit alone in your bed if she doesn't want to have sex with you. If they don't like you in that way, they won't go alone to your house at night. Very simple. Another answer is that the girls who are just faking-not-liking-it will lie completely still so that it's easier for you to take their clothes off, while the girls who really do want to take it slower will tighten up so that it's harder. If the subtleties of their actions are too hard for you to read, you can always do what I did and just stop every time they say "no": If they get pissed off at you for doing that, then they didn't really mean "no".
For whatever reason, Chinese girls often think that boys like to feel 100% in control, dominant and almost like an attacker. Maybe that's what Chinese boys like, I don't know. One girl I've been with would always yell out "what are you going to do to me? Oh no! It's going to kill me! It's too big, it's too hard! You must let me go!" but she'd be smiling and having a great time and would constantly come back for more. If she'd been my first experience and I'd heard her scream "please let me go!" I would have, well, let her go! And she would have been disappointed.
What I'm trying to say is that Western sex culture is not universal. The same holds true in many areas, beyond the "no means no" line. Before being in China I would have strongly supported the notion that a girlfriend or wife has no responsibility to have sex when she's not in the mood. But in China the traditional view is that a woman ought to (not must, but ought to) let a man take what he needs, as he is responsible for bringing in the money that will send the kids to university. The woman's job is to make sure the family and house are happy. If she's not putting out, the man won't be happy. I'm sure some women resent this approach, but many have been use to this thinking since childhood and are happiest when they perform their roles best. The same way many Chinese men will choose to work 20 hours overtime a week for an extra $10 to give their wife - a choice I view as utterly insane. In Canada I would hope my wife or girlfriend only has sex when she wants to and never feels forced; likewise I hope my wife understands I'm not going to work 20 hours overtime just so that she can buy an extra pair of shoes.
Cultures are different. Adjustment is difficult, but you're awfully naive if you think that sexual norms of the west are some sort of universal truth.