If today's explosions in Boston turn out to the caused by firearms powder, there will be calls to ban the sale of powder.
If high explosives, those already are not available for sale -- yet still, people have been killed and many others seriously wounded.
THE PROBLEM OF EVIL PERSISTS REGARDLESS OF THE SPECIFIC METHOD USED.
It is the problem of EVIL which needs to be addressed. That must be done with moral education, with ethics, with religious training, with philosophy, and -- first and foremost -- with two things admitted.
1. Evil EXISTS, has always existed, will always exist until the world is made new (NOT by the actions of humanity, ever).
2. Moral relativity is itself EVIL because it seeks to excuse evil "if we only understand; it's their way, their culture, it's just different, it's just as good, who are we to judge." NO.
We may not judge intentions or hearts; we MUST judge ACTIONS. Murder is wrong. Murder in the name of re-education, in the name of G-d, in the name of ideology -- is still wrong; is still evil.
That evil is not mitigated on iota if it is committed with a shoelace; it is not worsened by being committed with an IED. Evil is Evil is Evil.
Mankind has a streak of evil; Alexander Solzhenitsyn said the line runs through the middle of each human heart.
That is the proper place to fight the battle against evil.