You give Obama a "half-true", for a statement that you acknowledge is false. Apparently, the "half-true" comes after making a bunch of assumptions that he didn't say.
Now look at this one: http://politifact.com/truth-o-meter/statements/2011/apr/18/michele-bachmann/michele-bachmann-says-top-1-percent-pay-40-percent/
Bachmann also made a false statement, and you label it as such. But, if you assume she meant federal income taxes, it would be true. So, why not "half-true"?
I suggest some consistency. Either they are both "half-true", or both "false". Otherwise, it appears you are willing to give Obama the benefit of the doubt, but not Bachmann.