I've had issues with this as well.
My aunt is a grad of Davidson college, where they have eating houses instead of sororities. In their recruitment process, they have nights of parties similarly to sororities, but the difference is that only the freshman make the selections, and the placement is by lottery. My aunt thinks that this is best ever. She told me once, "Even if everyone in the group hates you and thinks you are a loser, you should be allowed to join it."
People bash selective social organizations all the time because of past injustices (ie, discrimination religiously and racially) and because they perceive that they are still based along class and popularity hierarchies. What they don't see is that Greeks are moving towards far MORE tangible standards than in the past--ie GPA, activities, etc. However I would agree that there is some room for criticism of Greeks. There are chapters that are interested in getting the richest and most beautiful members. Hey, those people probably fit in there, but it comes across (to many) looking like the ONLY reason they've been chosen is because of the money or looks, not the great personality and relationships the members have (again, less tangible to outsiders). So I see why people think the way they do. And I honestly have problems with the way some chapters think. I believe that there is still racism and classism in recruitment (clearly not for all chapters, just a few). We've come a long way--we still have far to go--but I think that people should recognize our accomplishments and realize that basically EVERY organization has membership standards. Even a club with open membership often makes the less accepted members feel uncomfortable.