I take the opposite view arguing something like this:

After an event like the bombings lots of travellers will stay away. That means better rates and less crowded facilities. So it's a good deal for me. It also means that the people who depend on the travel industry for their livelihood, and had nothing to do with the atrocities, need support. So my going is a good deal for them.

I would also argue (as NY did after 9/11 and London more recently) that at times like these one should support these areas because by staying away the terrorists are handed a victory of sorts. Of course this is based on the extremely low probabilities of being involved in such an event. I am definitiely not advocating going to into a war zone or an extremist enclave. And if the authorities are nonchalant about terrorism and tourist safety then all my sympathies disappear along with my business.