If I understand correctly, he destroyed a couple of guns that are "grandfathered" - you can legally have them, sell them within the country, but cannot import them.
/k/ being nuts for guns is pissed because they're Assuming: rare, expensive, and possibly have some historic/sentimental value.
Because at the time there were only around 20~ Dragonov SVDs in the country at the time and the price for one could range from $20k-$30k, and that guy found two and destroyed them.
And on top of #24, there were only 4 SVD-Ks in the country to begin with. He just destroyed 50% of the SVD-K supply of the entire US, all because he didn't understand the laws that would have allowed him to either keep them or sell them for a substantial amount of money.
He had two SVDs which are illegal to import, but due to grandfather rights, the SVDs in the picture are legal to own and sell within the US. As a result, the guns are very, very rare, and as a result can fetch $20k+
He destroyed 2 of them, basically throwing away $40k+, as well as breaking the law by illegally disposing of a gun, and shortening the barrel length illegally.