The AR-15 is a very capable and appropriate weapon for many different applications and that's why it is the most popular, best selling rifle in the United States. Other than the ability to easily mount accessories to it like lights and such, there isn't a damn bit of difference between an AR-15 and any other semi-automatic rifle. Banning them would do fuck-all to prevent violent crime, murder, and mass shootings. Banning them is a deliberate attempt to undermine, infringe upon, and neuter the 2nd Amendment to the point that it is impossible to exercise the God-given right to bear arms.
You want to reduce school shootings? Stop having children out of wedlock. Stop feeding your children anti-depressants when they act out because their father isn't around and mom is on boyfriend number 3. Stop letting the internet raise your children. Stop exposing them to sex and violence before their little brains have finished forming. Stop buying them Call of Duty and Halo, and other fist person shooter games for their birthday. Spend some fucking time with them. Teach them how to socialize with other kids. Take them outside. Teach them how to be a man. Discipline them when they make mistakes. Stop capitualting to their every want and desire out of guilt for your shitty life choices.