No, you're not obligated to support stupid policies.
But, as a libertarian, you are obligated to think through your characterization of them as stupid. How would a libertarian deal with the current threat, as you yourself described it?
"But I thought they [the terrorists] were already here, their sleeper cells are already here, their weapons of mass destruction are already here."If those facts are true (and I believe they are, specficially since every govt spokemans who talks about this issue says, "It's not if but when...) then regardless of what we do over there...we will reap the whirlwind."
Let us start afresh. Please, sir, what is the libertarian solution to this dilemma? By all means, let us hear it.