I agree, but unfortunately there's not much I can do at this point since people have already purchased it.
I'm thinking of making it contraband and replacing it with a less powerful rifle. That way all the previous purchasers will get to keep it, It just won't be available on the store and instead a new one on the store can be purchased. Other than that, the only other thing I could do is increase the price. 

Ehh, not so sure about the contraband thing. Gen. Pony tried that on Russia, which kind of ended up leading to a war. I'm not sure if you are referring to the banning of items used in trade in game, or just taking it off the store, but I would definitely steer clear of the first one. If some player based police force wants to try to ban items, using their own team, that is fine, as that can be taken care of. I think creating a server rule is another thing however. Oh, and also, I think the matamorez could probably be replaced with something like a Sabertooth, but changing pre-existing kits is always risky.

-Jack

Is there any plugins that can make matamorez can't raid bases?

Well I'd just make it so people cannot purchase it from the store anymore, people who have already purchased it can still use the kit though.
They can feel free to trade it among them I suppose, It'd just be unavailable on the store that's all and replaced with a less OP weapon.

And HongKong, I don't think there is atm