Well, I'd agree and disagree. As long as the continue to include the regulation of civilian arms inside a country,the treaty is a threat to our rights. As this letter makes clear, it isn't a serious threat because it will never be ratified by the current Senate; just as CIFTA hasn't been ratified in over a decade.
While relying on the Constitution adds an additional fallback position, the problem there is we were just one vote away from not having an individual right at all. There are at least 3, probably 4, votes on the Court right now who would likely have no trouble finding a UN Arms Treaty constitutional.
I think the NRA has a good approach on this. Both the UN and the White House know what is realistic. We can now see what their response is.