Your reference is as reputable as you are yourself. First of all let me tell you that all the Muslims believe without any doubt that although hadiths are sayings of prophet (pbuh) but after all he was a human and these words got to others through other people and therefore none of the Hadiths are 100% without a doubt. Quran is 100% without doubt whereas Quran's interpretation and translation again is not 100% without a doubt. So in simple words (before you get confused as I know you are a nursery student) Islam should be looked at with the help of these two sources together and if you know Arabic then that helps. Although even written records (Quran and Hadith) are still more reputable than any other religious scripture but still Islam�s beauty is not confined to just books, but in day to day practicality as it is not just a religion but way of life. You name any problem in day to day life, social, economical, physical and so on and Islam would have already given guidelines about that.
Now towards your hadith but with some back ground story,
Just like few people today say that American nukes saved millions (I don't agree with that but) same way at that time killing one man by the name of Kaab saved lots of others. The reason he was killed for was
treason and almost in most of the countries even now the penalty for that is same.
Finally not for you birdie as I know where your
reputable knowledge comes from, but for others here, this is the full story on another chat line someone posted for someone like you.
http://answers.yahoo.com/question/index?qid=20 090421034515AAmAa3k
Now next time give me the answer to my question asked earlier or I do not have any more time to waste on you.