The fact is: the US Armed Forces are more dependent on electronics than any other country, and this is the last weapon we ought to want to see being used.A non-lethal way to cripple the enemy?
If not using them would prevent other countries from not using them, your argument might be good. The truth is that our enemies will even use civilian airlines as weapons, and we'd never do that, either.
No it wouldn't stop others ever using EMP, but our using it will hasten the time others use it. The guys who ride around on camels and donkeys (remember Afghanistan) are much better adapted to non-electronic combat.