Here is one reason: because it is part of the Marxist-Socialist approach. They abhor any gun ownership. They must not allow anyone, except the government, to own guns, so they can control the population and force its will on the people.
The Marxist demoCOMMIEs are not interested in protecting the people, they are interested in controlling the people. There's a difference!
Of course, your befuddlement is not unfounded. I am more perplexed at how ANY AMERICAN can support people who are trying to tear our country down from the inside out.
This was a Jorge Bush decision not a Demo one. Wake up to the liberal in the White House. Might as well have Clinton as the bunch we have now. You expected Clinton to do something like this.