I don't think that this is necessarily true. Throughout the 1970s, the British faced far more regular, and sometimes worse, terrorist attacks from the IRA. This did change the society, especially through the proliferation of cameras, but it did not turn it into a dystopia.  As a far more negative example, consider the US: on a regular basis, someone with a gun - usually a white man - massacres people on a massive scale. The US has refused to learn anything from this. Instead, it doubles down on its sociopathic protection of the Second Amendment and simply learns to live with massacres (so long as those massacres are not done by Muslims.). How a society responds to events like this attack is largely within the control of the society. It can overreact and panic and fall into an irrevocable tailspin, like the US, or it can adopt a more realistic but cautious approach, much like the UK did during the terror-ridden 1970s.