I'm currently only doing online racing on ACC public servers and actually I'm quite pleased with it.
2/3 of the races go quite well and there are usually guys to compete with. Some behave very well, some are a bit more on the agressive/optimistic side. I try to adapt. I think IRL it's the same. And from time to time there are exceptionally good battles - hard and clean.
However, I think its only possible in the top positions of the field (1st - 6th maybe). Further back in the field there are usually too many fools and it's pure luck to even get through lap 1 without major incidents.
If you are a couple of friends and competitive (as ist sounds like) odds are good that you already have a couple of guys on the server you can trust and fight with ...