OT: I found evil and good in every guild on Oblivion. There is no right way to do everything.
I was taught in my US history class (yes in the US) that the USA was quite evil to the Native Americans. It's widely accepted, at least where I'm from (in Wisconsin). The key to being good is to recognize the past mistakes of others too (in that case earlier in the country's history), to try and avoid repeating history. Even Vietnam was portrayed in a way in the textbook that presented the side of those who opposed the war as well. I know in some parts of the country they want to re-write history books to eliminate or downplay the bad things that our country did, but not where I'm from.
For me good and evil aren't always clear cut, but I think taking pleasure in the harm or suffering of another is always evil. That's not saying that fighting for a good cause is wrong, but taking outright pleasure in the suffering of another, no matter how wicked they are, is a pretty obvious facet of evil in my opinion. It's a bit harder when it's more grey.
I don't buy the whole "it's cultural" baloney though. I don't care what culture it is, a wicked act like genocide is pretty darn evil no matter what. Torture is an evil no matter what.