To me, the problem with these weapons is that they are much more likely to be deployed in a domestic situation. The military would have a difficult time using deadly force on an American crowd. But non-leathal weapons are much more palatable to the politicians.
There is a limit on how effective I want our military to be in terms of crowd control and suppressing dissent. If these weapons are perfected overseas, it is only a matter of time before they are applied at home.
Remember the bunny scream tapes used at Waco?