Well, you can partially blame the NRA for the mag-cap ban, simply for not having the intelligence to properly fight its enemies. During the eleventh hour when it was clear the anti-gun lobby had enough votes to pass the Crime Bill, the NRA was approached by legislators with a compromise. The idea was the NRA would remove opposition to the bill, and in return the mag-cap provision would be removed and a couple firearms such as the AR-15 would be removed from the assault weapon list. Instead the NRA refused based on principle, and as a result the bill was passed. Some gun companies (Glock in particular) were outraged that the NRA didn't take the offer.
One may indeed say the NRA needed to make a stand based on principle. However, ideology aside, which would you have rather been- a British soldier at Dunkirk or a German soldier at Stalingrad? Both armies were faced with total annihilation. The Britsh chose to retreat back to England. Years later they triumphantly returned to the beaches of Normandy, once their forces had been rebuilt and had recovered and had a powerful ally on their side. On the other hand, Hitler would not allow his troops to retreat under any circumstances, and as a result they were nearly completely wiped out by the Soviet Army.
When the anti-gunners are faced with certain defeat, they try to make a compromise with us and often get it (look at the Firearms Owner's Protection Act and its machine gun ban add-on for an example). Yet when we are faced with losing, it seems we'd rather be wiped out than cut our losses and try to minimize the amount of lost ground. Yeah, the Second Amendment is not something to be bartered with. We still have a mag-cap ban. The answer here is to wait until something comes along that they want, such as another kiddie safety law. When we see something that we feel we can live with, we'll then say "okay, but this is what WE want....."