As I tried to explain to the OP when he was complaining online, SMGs aren't weak and you just need to practice. As for saying "SMGs are useless against the best rifleman", that isn't even a point? Tanks are useless against the best faust trooper behind them, planes are useless against the best AA gunner if they don't see him in time, etc. Every weapon has strengths and weaknesses and there are situations where you are at a huge advantage or disadvantage due to your weapon - the trick is to consistently get into situations where your SMG is advantageous.
Learn how to use Single-Shot for the SMGs that have it (all Thompsons, Beretta, both Stens, and the Grease Gun may as well have it with the rate of fire). This helps a lot at longer ranges.