You're absolutely right, and people are being very hyperbolic. However: Obama's power to launch a targeted strike against an American citizen does not exactly "

You're absolutely right, and people are being very hyperbolic. However: Obama's power to launch a targeted strike against an American citizen does not exactly "derive from the AUMF." It derives from the Obama administration's interpretation of the AUMF (and other law). That interpretation may or may not be constitutionally correct, and at no point was this administration forced to argue the constitutionality of the strike before carrying it out. Even if we accept that the AUMF granted Obama the right to kill an American citizen abroad, Obama is making constitutionally controversial decisions without oversight. Although the white paper justifying the Aulaqi assassination did not argue that the assassination of non-Al-Qaeda citizens within the U.S. would be justified, many people are concerned that this sort of oversight-free executive decision-making sets a bad precedent, and that eventually some president might use similar arguments to justify drone strikes against American citizens.