Clearly the right-wingers do not understand the concept of "trade-off" or "cost vs benefit" (which is odd since they are usually so supporting for the market which is all about that stuff).
And yes they (right wingers) understand the idea of trade-offs. Don't talk to people like they're stupid. You might feel all high and mighty, but that's a fantasy. (Or did you think you were actually convincing? I don't get your behavior. Why would you act so stupid so deliberately?)
Anyway, the cost of removing the freedom to own a machine gun/grenade launcher/hand gun is small since almost no-one will ever use such and item for useful purposes and most people have no desire to own one.
To say that you have the right to bring men with guns and lock people up in cages who have not harmed others because you "calculated" that this policy produces a more optimal society is complete conceit on your part. Also, to actually carry out that act is immoral.
Do you have any questions about this concept and why some consider it true?
Another thing that you should ask yourself (since you're a utilitarian, you need to figure out precisely what is worth optimizing) is whether you value lives too much. If you could mandate that everybody do one hour of work each in order to collectively save 50 people's lives, would you do it? How about thirty minutes? Five minutes? What if we had the option to pay ten dollars? One dollar?
(Hint: The actual utilitarian answer depends on how old the person is that you're saving. And a dollar each is too high a price.)
Suppose scientists estimate (or if they're sociologists, suppose they pretend to estimate) that fifty lives per year (in the US) could be saved from mad gunmen if we outlawed assault rifles. (Yes, I know, this is an unrealistically high number, but this is just an example.)
So my question for you is, are you willing to pay a dollar for the right to use assault weapons?
I hear you can save the life of a starving Ugandan child for 11 cents a day. Suppose assault rifles are legal and 10000 of them exist in the U.S. Therefore each is responsible for 1/200th of a death. In that case, a tax of $0.20 a year could be paid for each assault rifle you own, which will go to starving Ugandan children. Hey, let's round it up to $1.00. We'll save over 250 Ugandans.
Would you support such a scheme, or are American lives worth more than Ugandans'?