Movie ratings are screwed up in our country

There is something completely hooey in our rating system. Case in point : went to the Green Hornet two weeks ago. Rated PG-13. Went to the King's Speech tonight. Rated R.
Walked out of the Green Hornet thinking there was a WHOLE lotta violence in smooshed human carnage. No blood splatters, but you see people get smashed and killed. It is somewhat presented as a kids movie, and I saw it with our son and a friend of his. I actually covered their eyes at a part. (they were nonplussed about the whole thing, and humored me)
The King's Speech R rating? Well I imagine it was because he says the word fuck and shit when overcoming his speech impediment. That was it. No skin, no violence other than raised voices.
PG-13? Multiple deaths. Shooting. Sex (implied, not shown). Scantily clad babes moving to the beat and drinkin' alcohol. Drug selling. Hitting. Guns. A gang attacking a woman.
Here is where I get all crazy talkin'.
Why is it okay for our children to become immune or at least comfortable with watching violent acts -- something that they may not ever see or be a part of in their "real life" -- but sexual material and language are taboo? Sex which is vital for our species, and bad language which pretty much everyone will be exposed to in their lifetime...
WTF? Makes me really cranky. I read somewhere that our movies become more violent in times of war. To keep our adrenaline up? To keep us on the aggressive?
As an aside. I loved both movies. The GreenHornet was tapping into my old crazy love of cars. The car is genius. Had a bit of chitty chitty bang bang coupled with the batmobile.
Rose went with me to the Kings Speech. Boy, did she ever NOT want to go. But she was surprised, and loved it. Mr. Firth rocks.