The reason is a tempting, very specific faith-based ideology. Generally, people are not born with an innate desire to obliterate innocent people. Generally.
Now, admittedly, I don't believe criticism of religious ideology is equivalent to prejudice. Why does any belief deserve dispensation for its stunningly illiberal outlook of, say, the role of women in society? In Egypt's Tahrir Square, the epicenter of the anticipated democratic nation, a mob of God-fearing men aggressively descended on the women there on International Women's Day, intimidating and abusing them.
Sometimes it seems some people are more concerned with admonishing political incorrectness than they are with rebuking overt intolerance.
And though I am skeptical that King's hearings will accomplish anything constructive, the obfuscation of his goals is, in the end, more harmful than the hearings themselves. Because it's the critics who have falsely transformed a ham-handed congressman's hearing on radicalism into an imagined referendum on all American Muslims. Which turns something useless into something incendiary.