I have been wondering about this since the weekend. Ds's grandad often plays rough and tumble games with them, which they enjoy and request. In fun my younger ds (in particular) shouts 'no, stop' but it is clearly in fun as he is laughing at being tickled or held down or whatever.
The thing is that this set me thinking about the example this was setting in terms of behaviour when people say 'no' or 'stop'. I always tell my boys that if someone says 'no', 'don't' or 'stop' then it means that they should do as they have been asked - more to teach them for future dealings with girls than just yet tbh. But obviously this activity with their grandad is not reinforcing this message.
Come on it is clearly a game and the child understands. Now when they get older and get into a romantic situation with a girl it will be clear if the girl is laughing saying stop or crying saying stop.
I think you need to put this in context a bit. it really is a very very small minority of people who grow up to hurt or rape anyone. Most people grow up in a world of complicated mixed messages and are still magically able to understand perfectly easily when no means no. This is a pretty common game you are discribing with the gp so I really can't see that there is any real risk at all of it causing a problem with your kids when they grow up.
And I am going to throw in a for good measure and because you surely win todays award for parent paranoia