What people need to recognize is that Free Aim is a higher difficulty setting. I played an Auto Aim mission with a friend once and laughed at how easy it was compared to playing it Free Aim, it was ridiculous.
I mean seriously.
In an auto am gun fight.. You can jump on a car hood and auto lock spam kill every f*ckin AI in sight in 2 seconds.
Try that in free aim, and you would be lucky to kill one AI before they killed you.