This might sound obvious, but it seems like it needs to be said.
There is a judgement to be made. Loss of freedoms and liberties vs. protection from attack. We make this loss of life to benefit judgement all the time. We sent troops overseas, knowing some will die but judging it a worthwhile sacrifice. People die in road accidents, but not enough to make us want to ban cars.
In London, 52 people died in the 7/7 attacks. Unlike the examples I gave, that was a one-off event, not a yearly loss. Even in 11/9, only around 3,000 people died compared to over 11,000 a year from gun crime in the US, and again it was a one-off event. There is simply no way to argue that terrorism is deadly enough to warrant taking away fundamental freedoms from millions of innocent citizens.