The "Benign Violation Theory" of humor explains this well - basically, that humor results when we simultaneously perceive a violation of "how the world 'ought to be'" and realize that the violation is benign (http://en.wikipedia.org/wiki/Theories_of_humor#Benign_Violat...).
Thus, something one finds funny can be not-funny to another either because it appears dangerous (offense), or because it seems normal (meh). This correlates with how closely or exclusively one feels the "norm" that is violated.
It's interesting to analyze why I find jokes funny or offensive (or funny in spite of myself), such as self-deprecating humor, puns, racial/religious/dirty jokes, etc.
Although this can explain why some are offended when others attempt humor, it in no way excuses including offensive content - the point is to be sensitive to the feelings and values of others. We should work both to avoid giving offense, and to be tolerant when others offend without intent.
Thus, something one finds funny can be not-funny to another either because it appears dangerous (offense), or because it seems normal (meh). This correlates with how closely or exclusively one feels the "norm" that is violated.
It's interesting to analyze why I find jokes funny or offensive (or funny in spite of myself), such as self-deprecating humor, puns, racial/religious/dirty jokes, etc.
Although this can explain why some are offended when others attempt humor, it in no way excuses including offensive content - the point is to be sensitive to the feelings and values of others. We should work both to avoid giving offense, and to be tolerant when others offend without intent.