I'm praying to God that is it neither:
1) A right-wing Militia radical, who chose to attack on Patriot's Day
2) A left-wing Occupy Wall Street terrorist, whose chose to attack on Tax Day.
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Why?
Because if it is a domestic terrorist, the government will use it as an excuse, with BI PARTISAN SUPPORT to strip more of our liberties for more FALSE security.
If it's a domestic terrorist, we all lose, left and right, because the Government is the only party that will gain from this massacre; the people lose.
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If it's a foreign terrorist, then it allows us to make the argument that all their Liberty-stripping Laws, like the Patriot Act and the NDAA are useless, and it would against the government, not in favor. However, we would have to be vigilant and active, otherwise the government will still use it to their advantage, but at least we have a good fighting chance to stop them in this scenario.
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Now let's consider the ONLY two possibilities concerning this terrorist attack.
1) The Government had no idea that is going to occur, therefore their Anti-Constitution policies don't work.
2) The Government did know it was going to happen, therefore they let this happen so they can take more of our liberties away.
Either way, both 1 and 2 are strong arguments AGAINST the government expanding its police state powers, because either they knew about it, or they didn't.