I'm no ballistics expert, but wouldn't over penetration be less of an issue in a home defense situation than an AR in .223? Also, not to mention, the 'ire' that has been generated seems to be more about your assertion that shooting a rifle at any distance less than 400yds is a waste of time. I vehemently disagree with that assertion. Its not a wast of time for a few reasons I can think of off the top of my head:
-it's fun
-trigger work practice
-not everyone has private land or access to a 400yd + range
-etc...