People use the guns they want to use, even if they use OP guns you can't force them to use anything else. Only players who enjoy the most challenge use weaker weapons, FMG9 akimbo, P90 and PP90M1 etc are for people who either want to be jerks to others or just don't give a single ****. Or they just want to be badasses and own everyone.
I personally never found anything fun about taking OP gun and beating up everyone with it, it was boring and I'd end up getting lower streaks because I got too confident and tried too hard with them most of the time.
But yea, use the weapons you want to use and if just possible then get so good that you can beat every single OP weapon user. I personally counter most opponents with more advantage by using my head, C4 when you're in a combat against a player who thinks he is clever by running behind a corner and ambushing you is lovely way to make people rage, seriously, so many people think they get an advantage of going behind corner to wait for you, that works only against the worse players.
