Because they argue one thing while admitting the opposite

As I stated before "the NRA on one hand complaining about the increasing number of gun laws yet on the other hand claiming that less gun control equates to less crime when crime rates have been falling over that period" is hypocritical. You admit you see my reasoning. Whether they are wrong or not is a matter of subjective judgement. I believe they are wrong, others may not.

Who are you begging to differ with when you write "As for your argument that crime has dropped as gun control was raised, I would beg to differ"? The link you provide can be countered by links to other reports claiming the reverse of what Kopel claims. We can all easily summon up reports that concur with our thinking.