Extreme Positions

Why is it that when we are convinced we are right often that we think those who do not agree with us are wrong?  Why is it that we think the other party is the one who has drunk the proverbial Kool-Aid and not we ourselves who have imbibed the spiked libation?

I find often that when we are strongly moved to one end or another, finding ourselves taking extreme positions to unseat those who disagree with us, it is we who are unbalanced though we can not see it.