How do I deal with my friend's brat children?

Most of my friends have children who they have absolutely no control over. I love my friends, but their children are awful little savages. My two sons are well behaved and well balanced, so I must be doing something right. I can't understand why my friends all just let their kids behave badly and never reprimand them whenever they get out of hand. Sometimes the parents make empty threats and their kids just carry on misbehaving knowing that their parents will never follow through or do anything about it. When they come to my house I first wait for the parents to sort their own children out and when I see that they don't, I feel forced to step in, because it is my house and I want some law and order. When I tell their kids off the parents look shocked and embarred or take offense and try to defend their kids behavior and their kids show their anger towards me by either sulking or ignoring me. How on earth do I deal with this, without making myself unpopular. I don't see why I should stop seeing my friends, just because their kids won't behave, that would be giving in to their children and letting them have their own way, and they are spoiled and pampered enough already. Why don't parents deal with their children these days, why are they so afraid to discipline their brats? My friend's refuse to accept my advice or suggestions about parenting, instead they change the subject or defend their children s behavior or take offense.