You should understand, that of those 488 currently in DR, only a small fraction will ever be actually executed. It's practically the same as life term. I hope you are not against that either? The "endless insecurity" is actually deliberate, because people (majority) will actually oppose the abolition of capital punishment.
Tangentially, how should a country (read US) deal with terrorists (in the strictest possible sense of the word) who planned and carried out significantly impactful attacks against their citizens?
Its probably not being downvoted for that reason. Rather because you're just being plain wrong here.