If you now say „we must take even more liberties away, to have even more security“ then you are basically doing what the terrorists wanted you to do in the first place.
Yes, we do need to fight the terrorists and their inhuman ideologies of hate and murder. Yes, we do need to protect people from violence. But we also need to preserve what makes our society worth fighting for, and that is freedom, human rights, democracy and an educated understanding of the fact that it is our differences that makes us all unique, precious and yet alike, at the same time.
As for you, terrorists: you can kill people, but you cannot kill our values. You can spread violence, but you cannot stop our compassion and solidarity. You can spread hate and fear, but you cannot take away our freedom. You can fight, but you will never win.