I'm afraid ethics have nothing to do with it.
If a major force does not add AI capabilities to their military, the others will. It's a new cold war arms race. So you have to do it. There is no ethical discussion to be had where the outcome is that you refuse to do this on moral grounds.
So when you have to do it, there's only a few candidates that can. Google is the logical choice as it has the least business in China, unlike Microsoft.