That is exactly what CNN wants you to think. Please don't fall for it.
Apart from any arguements about unconsitutionality, as well as plain old uselessness of any gun ban (terrorists, just like criminals, do not obey laws), consider just how much more of a threat this rifles actually is over, say, my .300 Wetherby. The real world answer: not much.
Granted, my Wetherby does not have a 1700+ yard range, but that shot was also an extreme example of a .50 BMG shot. It took tremendous skill, but also more than a bit of luck. Also, how many firearm attacks in the U.S. have ever been done at anything approaching that range? None. The D.C. snipers hit their targets from less than 100 yards, and used a much smalle, cheaper, and concealable (and therefore more dangerous in the real world) rifle. More to the point, just how many sniper opportunities out there require anything near that range? I don't know about you, but in my home town, it's hard to get a direct line of sight for further than 200 yards, which is more than short enough for even a .223 like the D.C. murderers used.
The .50 BMG is so much overkill for any practical use by a terrorist (not to mention expensive and relatively rare), that its very size and weight become its major liability for the sort of uses a terrorist might consider putting it to. For the same money as a single .50 BMG, al-Queda could equip about a hundred terrorists with cheap, small, relatively easy to transport and conceal AK's (and who knows how many explosive devices), which has a much greater potential to cause terror and damage than any single .50 BMG.
The .50 BMG rifle has only a very limited use militarily (though it is imminently suited to that limited use). Unfortunately for the case of the would be gun-grabbers, that specific military application is not suited to the motives, goals, or budgets of terrorists. It's very good for shooting terrorists from a fixed and defended position, but not so very useful for terrorists shooting from an unfixed and undefended posision. Additionally, the capabilities of the .50 BMG are readily thwarted with some very specific but simple measures (see the presidential motorcade example in another post on this thread).
An unjust and unconstitutional ban would not do anything to protect anyone from terrorists, but would only further erode the rights of law abiding citizens.
That was a beautifully reasoned and presented post. I am not sure I am convinced, but you raised a number of good points, and it definitely was food for thought and reconsideration.