That's because 80% of all weapons manufactured today are semi-automatic. In similar news, most vehicular homicides are attributable to cars that have seat belts. Should we ban seat belts, or should we take a look at causality?
As for the criminals who engage in mass shooting, I think that we can agree that it's a disgusting, cowardly act, but we can't very well pass laws to prevent every crime someone might commit. As for "Exactly why mass shooters prefer high capacity weapons", that's not even necessarily true. The VA Tech shooter had 17 low-capacity magazines and just reloaded whenever he felt the need. Again though, per DC v Heller, standard capacity magazines are 'in common use' and 'for lawful purpose', which means that effectively, on Constitutionality, should not be bannable.
Regardless, of all the homicides that have been committed, the vast majority are perpetrated with handguns, not rifles of any sort, and nobody is moving to ban those in any way. Moves to ban guns based on their aesthetic features is, in my opinion, naive. Banning guns with "military style features" like barrel shrouds (that exist on every rifle made since 1880) or sliding stocks (which simply allow a gun to be shared by people of different stature) are akin to banning cars with racing stripes or bucket seats.
It's also pointing out that while mass shootings are indeed terrible, the citizenry in the United States has had access to the same type of weaponry since 1936, and these school shootings are a relatively recent phenomenon. The weapons themselves are certainly not to blame, so I believe we should look for other causes.
"Most victims of mass shootings aren't afforded that luxury."
Nor are they generally afforded the luxury of being armed themselves. Every mass shooting (except perhaps the Gabby Gifford shooting in Arizona) in the US since 1950 has been perpetrated in a "gun free zone" (not yet sure if Dormer counts), where the citizenry would be expected to be unarmed.
The Aurora, CO shooter for example, bypassed 6 theaters nearer to his home, including the largest theater in the area, and instead effected his spree at the one theater that enforced a gun free zone. Virginia Tech, Newtown, Columbine, Fort Hood, etc. The elimination of gun free zones may prove effective at deterring mass shooting. Despite the President's scoffing at the NRA's suggestion to put armed guards in school, he has effected that very policy through executive order, so perhaps that will mitigate shootings as well. Others have suggested that we investigate the link between mass shooters and prescription medication, but I can't speak intelligently on the subject myself.
"People print counterfeit money too but we put measures in place to minimize it."
So, perhaps I didn't make that remark with the care that I should have, but nobody is seeking (except perhaps California) to ban the possession of magazines, but the sale and import of those magazines into the state. Using my home state of MD as an example, I am not allowed to buy 30 round magazines here, and similarly, nobody here is allowed to sell them to me. But I can cross state lines to Pennsylvania or Virginia (which is no more than 20 minutes in either direction) and buy them and bring them back in without violating any laws whatsoever. Moreover, I can buy magazine "parts kits" from anyone I choose, on the internet or even in state, and then I just have to assemble them, which is a fairly trivial endeavor.
That there are also federal provisions that allow me to manufacture my own weaponry for personal use would mean that banning the sale of high capacity magazines would be particularly ineffective for too many reasons. 1) There are literally millions of them already in existence in the United States, 2) anybody can download a template and print them off in a 3D printer, 3) Criminals planning to commit crimes like mass murder are almost certainly going to ignore any such statutes, 4) Limiting capacities to 10 or below hasn't proven to be effective in reducing the body count even in cases where the criminals chose to use them and of course 5) It would almost certainly be an unconstitutional provision based on recent case law precedent.
Edit: Note, I made this reply before you edited to add your rhetoric about negroes, "Free negros were also unconstitutional at one point. The constitution means nothing to me."
In hindsight, it makes me wish I hadn't bothered to respond at all. Kudos for having wasted a good deal of my time.