I think you misunderstood a couple of things. By "badge", I didn't mean something like a scarlet letter that will color people's opinions, but rather something like a merit badge — a trophy of success and achievement. A very low rep is a badge of that sort, and by discouraging extreme downvoting, it will be less likely for trolls to achieve.

[posts with reps of -1 or -2] won't end up in worst nodes

Actually, they frequently do make the "of The Day" list. As I'm writing this, only the top 2 (of 10) worst nodes of the day are more negative than -2. I don't know how long such posts typically sit there.