I can tell you that this is NOT 100% true. Mine (especially my dominant male) gets into lip locking a LOT, ESPECIALLY with my EBJD. Fins get a little torn (more theirs than the EBJD) but its nothing serious or major.They also have a different way of reacting to threats. When adult Rainbow cichlids meet a threat like from a larger cichlid like severum, they often go into a submisive head down attitude. Sometimes it works , sometimes not depending who the threat might be. They do not fight. They bluff, make charges, and flare out their gills, but don't tear fins. If the intruder doesn't leave they will go to the side and push rather than biting.
I do agree with you though that cichlids get a bad rap and are very misunderstood. I think its just a matter of knowing what the different species are like, and knowing the dynamics of the individuals in your tank.
I also 100% do NOT agree with any notion that you cannot have any cichlids in a planted tank...its a little harder sure, but its definitely not impossible.