I dont know if this has been suggested anywhere else since im not reading 7 pages, but here it is.
Whoever wants to get this achievement "Starting a Riot" , I have a very easy solution...(if you dont have a partner).
First of all, if your like me & cant always have your "online co-op buddy" help you out, or just dont seem to have someone to do this with, i have the solution. First of all, get your 2nd controller out & load up another profile. Do some split screen action on Recruit & load up Mission 3 (the mission where you have to save Eisenhower).
1. Head up the hill with your profile & leave your 2nd player sitting down at the start, you dont need him yet. Once at the top of the hill, snipe the guy on the turret & kill whoever else is in your path, but leave everyone else alive. Move towards the building that the turrent is on top of, & you'll see a riot shield on the ground near the fork-lift or whatever it is. Go over to that barricade & wait there.. or wait behind the tent.
2. Grab your 2nd controller & run your other character up to where you are. Run over to the riot shield, pick it up & walk as close to the barricade that you can so it doesnt take any damage.
3. Grab your 1st player controller, & run up behind the '2nd player' to get in the 'riot shield mode'. You wont take any damage since they cant hit you, & your shield wont break since they cant shoot it. Simply adjust when you need to with 'player 2' & shoot everyone with your profile to get the achievement. Now since its at the start of mission 3, you just have to restart misson or check-point until it unlocks. You should honestly get at least 10-15 kills every time you do this.
BOW TO THE KING
LISTEN TO METAL