To continue preconceived notions, people turn to manipulating language to achieve a mirror effect in regard to their beliefs, particularly when discrimination is concerned. In the twentieth century the word "gay" came to mean homosexual, an action people who fit the description; after that point the word was commandeered by the homophobes, coming to be a synonym for bad. Today, even among society's more accepting members, it seems to be that the twisting of  a once innocent word has no negative connotations- hence the concept of "acting gay" isn't challenged. Failing to see the problem therein is akin to not understanding how "niggardly" could be construed as an offensive term.