People play single player and feel themselves as absolute aces and then the rude awakening of the multilayer brings them down a notch and produces cognitive dissonance that leads to them talking about cheating... People are much better than the AI ok?
Its the same story with BF3 -
There are quite a lot of people who are AWESOMELY better then you, just admit it and try to improve. If you give a firing solution to your enemy, expect to die - simple as.