CBS News confirmed Abedi was known to British authorities prior to the attack. (emphases added)It turns out most terrorists are "known to the authorities" prior to their violent acts. This is so common the media has developed a term for them - "known wolf" - wordplay on the trope "lone wolf."
FDR understood the wartime trade-off between civil rights and security; the result was internment of thousands of people of Japanese ancestry - citizens and aliens. They had done nothing wrong yet, and most probably never would.
Jihadis have declared war on our Western "crusader" society. At what point do we stop letting known suspicious characters run free until they do something awful? Perhaps we could consider deporting immigrants who are known malcontents and interning jihadis born here?