On the contrary, the difference between the Mafia and Coca-Cola is that Coke provides its product on the open market, without using violence to defend it's turf against Pepsi, and if it did, people would quickly stop buying Coke.
Perhaps this is more clear: the differences between Coca-Cola, the Mafia, and government are differences of degree, not qualitative differences.
Right people would stop buying Coca-Cola in that scenario. But if a gang started being as civil to its competitors as Coke is to Pepsi, then that gang would lose out fast. If the U.S. was as nice to England back in 1776, the U.S. would have lost out.
You might be surprised... (some) Bloods and Crips have agreed to a truce, and are doing just fine. I think the US probably did have to give England a bloody nose back in 1776, but, again, dealing with government. All they understand is violence. Coke, on the other hand, competes just fine with Pepsi, and even all the other soda brands, and never once did I hear of a man in a blue delivery uniform shooting one in a red.
There's a distinct difference between Mafia and Government on one side, and private companies on the other. That difference is the market. Mafia and government operate in the red market, where violence is an acceptable fact of business. Pepsi and Coke work in the white market, where it is not.