your painting it out to be an obligation. someones a "jerk" for not doing it. a quick google search for "courtesy" yielded the following: "a polite speech or action, especially one required by convention." the use of REQUIRED fortifies my assertion. similarly, "obligation" gives us: "the condition of being morally or legally bound to do something." in this case, the 'doorstop' is MORALLY BOUND by COURTESY, under the fallacy of tradition. tradition, or in this case, convention: "a way in which something is usually done, especially within a particular area or activity." and the convention being holding the door open. ergo, by the definitions of YOUR OWN WORDS, one is OBLIGATED to hold the door open for another, for nothing more than a pointless tradition of groundless morality. and finally, respect is a two-way street; its something that is both given, and earned. again, why does one owe another anything, even as simple a thing as a second to keep a door open?