How do we know Glenn Beck isn’t Mumm-Ra?

Huh. Valid question, since he asked a Muslim guy to tell us the difference between him and a terrorist.
Daily Kos: Can You Tell The Difference Between Glenn Beck and a Sociopath?
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It’s not often that CNN Headline News host Glenn Beck runs across a point worth making — he is famously demure and objective, and not at all an intellectual thunderchud propped up in front of a television camera because CNN looked at their demographics and decided that appealing to the vapid, stupid and bigoted was a far cheaper way to run a network than any of the possible alternatives. But he has a good point here. How, indeed, are we to tell the difference between a brown person who is reasonable, and a brown person who is trying to kill us?
It is a troubling question, and one that got me thinking. How can we tell the difference between evil people and good ones, based solely on their race or religion? How is a reasonable person — like, say, a news anchor for a major media outlet — to know which ones to hate, which ones to fear, which ones to merely suspect, and which ones to give a pass to?