I wouldn't call the barbarians evil. Even when people "seem" pretty evil, that still doesnt justify murdering their civilian population. For example, in war, generally speaking occupying countries capture, but don't kill cities, or are called war criminals. With that in mind, i think razing any city but THE most evil (aka the ones that are worshipping demons, aka ashen veil) would be an evil thing to do. As it is, i would consider barbarians more chaotic than evil. They are tribal and warlike, but they don't have a goal of destroying the good, or preserving evil. So burning their cities down is still killing civilians that aren't pure evil, which still sounds like a bad thing to me. I dont have a real strong opinion about it, i'm just trying to make logical connections as to why things are the way they are, and how it makes sense to me.
Yes, I see what you are saying, but you are missing one important point in the discussion here.
That is that in the games the barb cities spring up like weeds. In most cases, certainly with the AI civs attacking barb cities, they are only population 1. You have no choice but to raze the city. It is clearly a good strategy to take out barb cities close to your borders. I don't think anyone will deny that. However, if you don't want to capture the city, or it is only pop. 1, it gets razed. Usually, I can Sanctify the city ruins and no harm done. However, the AI never does this. And, again, IMO, the counter increases too quickly.
The solution as I see it to solving this is to make razing the barb city have no effect on the counter. I think if the barb cities popped up a little less (on land maps as Niilo said), that would be a solution too. Kael tried something to fix this, but IMO it didn't slow down the popping of barb cities, especially those in the same location of razed barb cities.
As I said, if I had to choose between Good and Evil, I would say the barbs were evil. They certainly are not Good. But, I can also see how you can say they are not Evil. But, then again, is destroying and pillaging a Good thing?
So, let's call them Neutral or sorta NPCs that wreak their own brand of havoc, but do not impact the counter when their cities are razed. Frankly, they move the counter quite a bit on their own in raging barb games by razing enough cities.