A govt (NSA, CIA, etc) couldn't rent the services of a botnet through a third party and smash Litecoin with hundreds of thousands of nodes? Why build a warehouse of rigs when you can simply rent more far more hashing power as the entire Litecoin network has on demand. Also how many CPU do you think the a major government or bank has? They wouldn't need to build some ASIC chips, Litecoin provided a back door using hardware they already have sitting idle for 16 hours a day.
The cost to 51% attack Litecoin is negligible and could be done for free by a botnet operator who is just bored and curious if he can accomplish it. Making CPU more competitive (i.e. crippling more efficient hardware) would only make Litecoin even more at risk to operators with huge numbers of botnets.
Both BTC/LTC are vulnerable to such attack. Any gov has access to much more hashing power than both of the networks combined. The U.S gov as it is now has millions of ASIC devices, used for encryption. It wouldn't be to hard or even that expensive for them to decide to make BTC mining ASICs, and then crush the network.
Really, the only thing that keeps either coin safe, is its lack of recognition and underestimation. I would guarantee though, if Bitcoin, or litecoin for that matter ever got to the point where it could replace fiat (like many people seem to think it would) there will be at least one of the 196 countries governments successfully attacking Bitcoin/Litecoin.
When people talk about the evil gov interfering, they seem to automatically think of the U.S Gov, there are far more unstable/corrupt govs out there that wouldn't feel too bad about destroying BTC/LTC given a reason.