The Effect of Political Correctness on Politics

The late Charlton Heston once said, "Political correctness is tyranny with manners."
The rationale of political correctness (PC) is to prevent supposed minorities from being offended (the manners) -- to compel people (the tyranny) to avoid using words or behavior that may upset homosexuals, women, non-whites, the crippled, the stupid, the fat, the ugly, or any other minority group identified by those who define PC.  Its primary method is the redefinition or replacement of words and behavior in order to avoid offense, to be sensitive to the feelings of minorities.
Before we can examine PC and its effect on politics, we must first understand PC's origin and purpose.