I don't know whether this is a strong argument or not, but it is obviously a strong word: Java's fate will end with the same one as Neanderthals': extinction! :-)

Also show this one to your boss: Java's Cover, make sure he/she doesn't miss the responses to this Paul Graham's essay by Tim-Berners Lee and Trevor Blackwell :-) And this, and this should be enough to make your boss staring at your Java friend suspiciously :-)