(CNN) -- When a man with hands drenched in blood stands just feet away from the body of a person he just hacked to death, still holding the murder weapons, we want to believe he must be crazy. How else can our minds grasp the evidence that someone would carry out an act of such inconceivable brutality? We don't yet know all the details surrounding Wednesday's killing in London. But the fact is we have seen this type of attack before, and even before one of the suspects started ranting to passers-by, we had a pretty good idea what to expect. This killing of a young British soldier was not an act of insanity. It was part of a pattern that has struck in many parts of the world before. This was the product of extreme Islamist radicalism we have all come to recognize.
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Frida Ghitis: We want to believe hacking suspects are crazy to explain the atrocity
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Ghitis: But it appears, as it has so often, radical Islamist ideology fueled attack
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Islam, Muslims or terrorism are not the enemy, she says. It is this murderous ideology
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Ghitis: We need campaigns in Muslim communities everywhere against its appeal
An important element in the fight against this pernicious, callous enemy is a campaign to undermine the ideology's appeal within @placeholder communities everywhere.