In Praise of Precise Speech

I've always been a little fascinated by language. It's interesting, to me, that groups of people got together and agreed on what to call things, everything from a solid object to a transient feeling has a name. To my thinking, the mutually agreed on definitions of words is one of the cornerstones of civilization and therefore relatively important. Because of my interest in this subject, I am bothered by sloppy word usage, when I recognize it. When I recognize it, is the key phrase here. Not being the sharpest tool in the shed, or an English teacher, I am confident that I miss almost as much sloppy word usage as I commit. In spite of these shortcomings, I slog on, determined to better myself in this area.
Therein lies the subject of this post. Bettering ones self in this area is not a team activity. No matter how long you have known, been married to, been friends with, or been the father of someone, when you explain to them that decimate means to reduce by EXACTLY one tenth and what they meant was devastate, they're apt to take offense. No matter how well meaning your intentions or how noble your cause, to the people who don't care about such things, you are just an ass.
As a self acknowledged redneck and rube, there aren't all that many examples of this that drive me crazy, but there are a few. Obviously the decimate/devastate thing and also the usage of the word sociopath when psychopath is what is meant. I have a friend who will correct you every time you say theory when you should have said hypothesis, since he is right, I will accept his correction with gratitude until I learn. There are several more, but this is starting to bore even me.
The people who place little or no importance on precise speech will say "What's the big deal, as long as you know what I mean?" Maybe they are right maybe it's not a big deal. Except that people like Mario Coumo will try to redefine body armor as a firearm so that it will fall under the same restrictive laws that guns do. And don't forget the fine folks out in D.C. who decide it's ok to call Mr. Heller's pistol a "machinegun". Pistol, machine gun, it's all the same. What's the big deal?