At first, I thought of Sheldon in the same terms, and the "caricature" became more grating and not so funny. And to be fair, there have been some heartwarming moments he has brought about, paricularly in the last few seasons, so those would be good to catch up on.

However, I have begun to think of his character as someone who takes the science he knows as seriously as some people (like his mother and possibly memaw) take their faith/religion. If Sheldon thinks that survival of the fittest is a core tenet of evolutionary biology, which we have no reason to doubt, many of his "ruder" actions make sense. Since the resources he wants and needs to thrive can sometimes be difficult for him to obtain, it makes sense for him to do whatever he needs to do to obtain them. If that means being generally unbearable to those around him (who are ultimately in this theory his competition), so be it, he has gotten what he wants, and seeing to their needs is only secondary at best. However, when the other characters call his bluff and are willing to match him, he becomes a lot more willing to get along, since that peace will benefit him in the long term. About the only challenge to this theory is that so far he has no progeny to pass along these traits, so thus far this actions only benefit him and are pointless in longer terms.

Also, remember that he was raised in Texas, and as the stereotype goes, "Don't mess with Texas." Especially in his less politically correct moments, he may be acting on latent thinking from his childhood that hasn't grown up with him. Some of his actions may be somewhat expected in Texas, but are a little more dissonant in California.