Reciprocation. "How would you like it if it were done to you?" The Golden Rule. One of the most fundamental values of Western society. Fair minded. Inspiring.
And a concept both Left and Right appear to be hellbent on throwing away in favor of "collective guilt." The Left wants to tell us how one gender and one demographic is the fount of all that is wrong with society. The Right wants to tell us how a faith whose members are a tiny minority will succeed in overthrowing the entire West when the nuclear-armed Soviet Union, with all their infiltrators, spies, propaganda and armed forces failed to do so.
This is the value of being a centrist. Don't buy either side's BS. The Right is sometimes right. The Left is sometimes right. But when both abandon principles in favor of tribalism and preach "my side right no matter what" they are both wrong.
Collective guilt is always wrong. If you champion it against the groups you don't like, you destroy all moral credibility when arguing for it not to be used against groups you DO like. A person is responsible for their deeds and their deeds alone, not for the deeds of their race, their creed, their nation, their gender etc. etc. We punish those who do wrong. We do not (without undermining our own laws) punish those who MIGHT do wrong.
Each and every one of us MIGHT do wrong.
If you attempt to argue against condemning all Muslims but simultaneously condemn all white men or if you argue for banning, expelling and surveilling some populations but not your own you are merely advocating tribalism, abandoning the principles which you claim to defend and condemning yourself to a future of ideological stalemate depending on who wins the vote. (Or do you imagine that your ideological opponents will just go away and die? Why would they, when you will not? If you make it a fight to the death, why would they not respond in kind?)
What are some answers to terrorism sans collective guilt?
Terrorism has two significant axes: Military/policing realities and ideological buy-in. The latter deals with neutrals in the population who are not (yet) a threat nor inclined to aid those who are. The former addresses those who cannot be reasoned with.
To the former, increased spending and greater intelligence sharing among Western allies is mandatory. You will have to kill those who cannot be contained or stopped. We will need more dollars for infiltration and disruption. It may be time to consider an Interpol of counter-terrorism. We will have to talk freely about civil liberties and technology (especially encryption and the communication it facilitates) and what we plan to do to safeguard liberties while addressing the threat.
Terrorism is a policing problem. The FBI has already succeeded here. They have a track record of disrupting the most violent, pervasive terrorist organization in US history-- the KKK, which bombed, murdered and brutalized its way throughout America and enjoyed broad political and popular support-- by infiltrating and honey-potting would be terrorists once funding and the political will was there.
As to the latter issue, buy-in, the US won the war of hearts and minds against the Soviet Union in part by arguing a better way of life. Piping Jazz over the Iron Curtain. Inspiring defectors. Arguing human rights. Nixon and Kruschev in the kitchen. Perfect? No. Undermined by greed and lies at times? Yes. But an argument which inspired in a way which idiots promoting meme wars and green frogs seem incapable of understanding.
ISIS promises glory in the great beyond. The West needs to uphold its own ideas of prosperity and equality under the law for ALL citizens to provide a superior vision attainable right here and now. Terrorism experts have opined that the US does a better job of this than Europe, but work remains. The GOP's open assault on the right to vote, demagoguery, winking and nodding at bigotry and failure to condemn outright lying and bullying by the President of the United States (see targeting of London's mayor as the latest of countless examples) destroys this advantage.
The Left has a chance to show the way here, but must transcend its own poisonous, identity-based ideology. Integrated communities adopt the host civilization, changing it and being in turn changed by it. Their members believes in the justice system, help law enforcement, defend their adopted nation (even enlisting to serve it) and even turn in their own lawbreaking family members. All of this is undermined by a Left which believes in ideas of cultural theft, which frames dissent as existential violence and which nods and winks at political violence so long as it is aimed at undesirables (aka punch_a_nazi.jpg).
TL;DR: Collective guilt sucks. If you promote it, you have no answers.
And if you go right wing, drive the bigots out or they will overtake you.