What is the reasoning for keeping assault weapons legal?

On the recommendation of some of the posters here I've edited the post. I can't change the title, and therein lies one of the biggest issues with this thread. I did not know the distinction between assault rifles and assault weapons. I also did not know (or remember from middle school) the point of the 2nd Amendment as it applies to Militias.

Anyways there are some good discussions going on in the comments so do carry on with those.