langurmonkey: Yes, being abrasive and impolite to people is a huge hindrance but people should stay loyal to who they are inside, no matter what.
The thing is, you should question this mystique a bit. You're not yourself, you haven't been faithful to yourself since you were born. You have "betrayed yourself" by learning to go to the toilet instead of shitting your pants, by learning to say hello and thank you, by learning to brush you teeth, to wait for the diner, to eat dessert last, and not plug little rocks up your nose. You also "betray yourself" by not driving drunk, not groping people who arouse you, not punching people when you're in a bad mood. And you've "betrayed yourself" every time you've learnt something that has gone against your common sense so far, and changed your perceptions of things (earth gravitates around the sun, dolphins are mammals, etc).
In psy terms, you could claim that you "betray yourself" each time your superego censors your id, if you claim your id is your "true self". Socially, you "betray yourself" each time you're shaped by society, but the thing is : you've been constantly shaped by society, there is no "true you at the state of nature", you have kept adapting to new sets of gratifications/sanctions, you have kept integrating new understanding of people, that have transformed your public -and private- begaviour. Until a point where, at worst, you've decided that some arbitrarily selected intemporal present is a "true self" and any further evolution or adaptation (in terms of "feedback feedback" or assimilated understanding) is a betrayal or an humiliation or a compromission. And you may have entered some mystique of worshipping this pseudo-intemporal self as the "real you", discarding the rest as false. A bit like xenophobic nationalists envision their country (or its near past) as an untouched culture suddenly threatened by change, migrations, and outer influences, without realising that what their represent themselves as an unchanged-so-far national identity is itself the dynamic product of such perpetual changes - a product that happened to be in place at the given time where they were born, and that they wish t freeze because it looked like it had been eternal to them.
The whole "be oneself" thing is dangerous. It presupposes that you are not wrong, or that if you're wrong, then you're right to be wrong. It presupposes that you have achieved some know-it-all state where there is nothing more you can learn, grasp, assimilate, that would justify a shift in behaviour. It's a glorification of conservatism in the most narrow and dangerous sense : it disqualifies self-questionning and evolution as bad things by themselves, because the present time (projected as an eternal static past) is worshipped as the pinnacle of everything that could be. And all changes (except most superficial, going in the same direction as current projects and intentions) are supposed to go downhill from there.
So, you should be wary about your pride to be yourself. As others point out, bullies, rapists, racists, wife beating morons, all can take pride in "being their true self" and "not letting others change their ways" and "being faithful to their outlooks". "I yam what I yam" can justify every attitude. It's not a value in itself, or a matter of pride. We're perpetual kids, in front of what there is yet to grasp in order to become a truly fair human, and kids can't go "this is my true self" to justify rolling on the floor screaming when they're being refused a candy, or picking up and putting dog crap in their mouth.
Now, there are things to fight for, and integrity is a very important value, because childishness can very well be on the side of the crowd exerting the "educationnal peer-pressure". The point is, being faithful to something has to be justified, defended, debated, questionned. Once you get all mystical, and decide to be fanatically "faithful" to something as evolutive and neutral as "oneself", something compatible with so many possible contents (every different "oneself" on earth), you just arbitrarily freeze something by cancelling any possibility of self-criticism and further amelioration. It becomes pure narcissism, and locks yourself in some eternal, circular, self-legitimation, whoever you are.
"Being oneself" as if there was some unquestionnable, pure, eternal "oneself" to be revealed and defended against any mutation, is a dangerous logic. Every person you used to be, from time where you considered that being fed was a matter of screaming loud enough, could have claimed the same thing to justify staying the same and to disqualify other people's expectations.