Bump drafting isn't cheating, it's just a tactic... I know it's been said a million times but still..
It happens in real life racing which allows it like karting, touring cars, NASCAR, etc. In things like formula cars obviously you won't see them doing that in real cars because they'd just break into peices. So in the case of formula cars bump drafting in LFS, well I think its just taking advantage of LFS' damage model...
I don't see it as cheating because its allowed in real life racing except that in some cases the cars don't allow it. I'm sure that if F1 cars COULD bump draft (and stay close enough to even have a chance at bump drafting) they would...