If you think that folks who disagree with you are, in general, corrupt or evil, this is a good sign that your brain has failed. Try rebooting, or purchasing a new one.
In my universally anti-groupist approach of pointing out that leftism, conservativism, and libertarianism are all coherent, important approaches to the world, I have found a leftism definition that appears more compelling than my standard one-liner. I'm still chewing on it, and find myself less than 75% in agreement, but consider it a very worthwhile read regardless. The author is eminent left-libertarian Gary Chartier, and the article is here.
Personally I score a solid 2/3 leftist...and I bet if Gary and I sat down for a cup of cream, we could hammer out our differences on Exclusion to a position we were both 85% happy with.
Politics are, at their core, ethical positions and statements about importance. Specifically about what is more important and less important. Gary may well have the best explanation I've seen about what leftism finds important. Check it out.