Hoist with their own petard

From Rantingprofs - Which Cliche to Choose?:

Honestly, the mind races. How about, "charity begins at home"? or maybe, "what comes around goes around"? Nah. That gets us dangerously close to "well the chickens have certainly have come home to roost." But it is a little hard to avoid at least thinking about that one looking at this marvelous headline from today's Times, "Saudis Support a Jihad in Iraq, Not Back Home." Gee, really sorry that hasn't worked out y'all. Guess it's dangerous to grab a tiger by the tail. (Oops! There goes another one!) But apparently what's good for the goose isn't necessarily good for the gander. All right, all right, I'll stop. But you tell me if that isn't exactly what this means:

In Saudi Arabia, a strategic ally of the United States, violence against the occupation in Iraq is seen by many as jihad, or a holy struggle, but virtually no one accepts violence as jihad when it unrolls here at home, in the heart of what is supposed to be the most Muslim of countries.

If you lay down with dogs, you get up with fleas.