Additionally, it seems to me like the gun control crowd advocate in the US is not going directly for the 2nd amendment, but instead trying to go for a route that will cause valid concern (5th and 6th amendment violation for the recent bill of "no gun if you're on no fly list", for example).

When I saw on Twitter today someone saying that (paraphrase mine) "it's acceptable for some people to lose their constitutional rights if we can prevent gun-related deaths", it's not hard to see how it might be a tough pill to swallow for the more right-leaning demographic, regardless of their stance on gun control.