I intended to write this some time ago so it's a bit late response.
I still don't get what you like about meson cannons. From small research (wikipedia) I've found that they would be okay weapons (I guess) in spacecraft-to-spacecraft battle but in atmosphere it would be more lethal to the shooter than the target. From what I've gathered this would either cause chemical or (miniature) nuclear explosions when coming in contact with baryons (that is, atoms) but here, it would instatly contact the air and explode in the end of the barrel (in similar way AM particle beam would act). As I said, I like my ground warfare particle beams loaded with baryons, thank you very much.
Other interpretation is that mesons would mess with the chemical or nuclear binds non-explosively (in this case, you'd create free radicals or ozone-like stuff), which would be even less useful as a weapon of war.
Anybody with actual physics major (zapkitty) is asked to correct my wikipedia science.
Regarding the sociology discussion and the fate of human race, I side with Stephen Hawking who said that if we will survive a couple hundred years more and make it to space, we'll be fine. Colonizing Mars and finally being able to mine asteroids would be a couple of incredible achievements for human race. These two would also ease up our "weight" here on Earth since we could use resources from other places besides Earth. This would in turn make our usable resources incredibly abundant so there wouldn't be a huge need to be selfish. And the extra living space for the some billions of us would certainly help.
I don't think we'll ever be able to get rid of wars completely. Seriously lessen the amount? Yes. Besides, in a way, our wars have been partly beneficial to us. The tech "level" graph goes *boom* whenever there is one and in case the eventual first contact will result in a war because they thought we looked at them funny, we'll be prepared.
Funny pics (humor never hurts, right?):
Whew... that took surprisingly long to write.
