I agree with NYC Native in some sense, but I think you are interpreting the quote incorrectly. Jefferson is speaking on domestic behalfs. This is more a support for 2nd Amendment (RIght to bear arms) than anything else. He is saying Americans inherently will fight for their rights. It is the governments duty to respond. It is also a warning to keep an open government so the people can see what is happening and not rebel. We have minor cases of this called "riots" but other than that, the people are happy enough not to rebel against the govt. He is speaking of civil war and revolt. As for foreign affairs, I believe the ends will justify the means, but that has nothing to do with this quote since we were not attacked by Americans.