If you watch F1s round Brandon from the grandstand, the top drivers nearly always make sure they're straight when they hit a car in front, you never see them making contact whilst sideways.
Think about what happens when you hit someone else's car with the front of yours whilst you're sideways - the forces are effectively the same as someone pushing the front of your car towards the infield, hence the back end will try and spin out, and you need more opposite lock to correct it.
I noticed some people were using full opposite lock just to get around the bends - this leaves you no opportunity for any correction if you do get tapped and you'll just be a passenger.
rFactor isn't perfect but it's a damn sight more realistic than Heat. It's up to individuals to decide if they prefer a more arcade game which is quite simple to master, or a more realistic simulator which will take much longer to get to grips with, but is so much more immersive.