According to Wikipedia, the term “whack-a-mole” is used colloquially to denote a repetitious and futile task: each time an adversary is “whacked”, it only pops up again somewhere else.

Not politically correct, I know: but it popped into my mind as I was reading about the horrific slaughter in Paris, France, today (7 January 2015).

The Muslims of ISIS are so afraid of dissident ideas that they kill those who espouse them. Only to have yet another dissident idea pop up somewhere else.

To use yet another colloquialism: it’s a mug’s game.

It’s also an ineffective way to win converts to Islam in the 21st century.