The rudeness is just a stage, my son is 5 and now everyone is stupid and he's started to swear....very mild but swearing nevertheless. It is yet another wonderful developmental stage and will pass. I'm afraid it comes from school and the TV.
I correct my son and have banned the use of the word stupid, so now everyone is weird. Try not to make a big deal of it.
As with the matters of identity, all kids get this at some point for various reasons, try and reassure them that they are different and special, but basically the same, I hope that makes sense.
Also it is true in some respects of menatl health issues within the afro-carribean community, however there is a lot of research that this is because they are just over represented, not that they are more likely to have problems but that they are more likely to receive treatment, therefore the figures are skewed.