"If you think you deserve the right to own all this powerful weapons, who are we to stop other countries from having them? This is a bit contradictory isn't it?"
Actually, no it isn't. Your analogy is not really valid.
Say, for instance, that I buy a surplus M-60 tank, park it in my back yard, and get a bunch of the neighbors together and teach them to be the other members of the crew. Neither myself nor my neighbors are violent felons, there is no reason to believe that we are going to attack anybody. We also put together a supply of main gun, coax MG and turret MG ammo. At this point, what our neighborhood now possesses is a credible deterrent to government run amok. At this point, nobody had actually done anything threatening. No assaults have occured in our neighborhood or in the town square using this tank. No response is warranted from the government, other than increased surveilance and a sure knowledge that our neighborhood has the potential to resist if it comes to that. We also have a credible deterrent against the next neighborhood's T-62 tank.
Now compare that to your country analogy. Those countries who we seek to limit their military capability are specifically those who have histories of misusing those same or similar weaponry. They have established that they are not intending to use those weapons in a defensive deterrent manner, but instead as a means for oppressing their own peoples, territorial expansion, and other aggressive purposes. Keeping with the analogy I had started, it would be as if the neighbors and I had fired up our tank, shot up the houses of the neighbors who refused to participate with us, and then rolled into the next neighborhood down the highway and started blasting away, destroying their T-62 tank in the process. Oh, and then rolled our tank down to the town square and blasted in the door of the bank -- all of this for no good reason other than we just wanted to. Yes, if that is what we had done with our tank, it would be quite right for others (who have more and better tanks) to seek to kill us or take our tank away and send us to jail.
"everything needs a limit otherwise can become overused, no?"
No. As long as government has the power, the citizenry needs to have that same power. This prevents coups by the military and representative governments from becoming dictatorships.