The majority of the critics/opposition doesn't have much substance to their 'claims' - or, they use points that are not an issue with anyone else.
There are certainly things Obama has done (or hasn't) that make him a bad president, but, he certainly is not the worst.
You also had a movement (and some still believe) that he is some sort of Muslim cell, that is here to do something bad to the USA. Muslim prayer curtains being forced into the White House. A forged birth certificate. These are all xenophobic - no validity to them.
There are also some things being done by his critics, that have no real basis and aren't panning out too well; such as Boehner's lawsuit for example - lawyers have twice now refused to handle it. And, the idiot is considering adding more things to sue the President over now,...
http://www.washingtontimes.com/news/2014/nov/14/john-boehner-mulls-adding-immigration-to-lawsuit-a/. Now, Boehner may very well not be a racist, but, why is he leading this lawsuit, when there doesn't seem to be much support for it? What is his drive for this? Yes, I am sure he has plenty of black friends, and he surely is NOT a racist, but his motivation is quite questionable.
Double standards are also another trigger;
- Obama gets no credit from things that happen on the battlefield; ergo, he had nothing to do with the assassination of Osama Bin Laden,... BUT, he is personally held responsible for when a weapons cache gets into the hands of ISIS,.... well,.. this logic does not jive; but, somehow applies to Obama.
His critics need to get their heads together and use logic, instead of knee jerk reaction verbal diarrhea - because:
1) it makes them look pretty stupid
2) gives the impression they are racist (which, does not exist and is totally not true, since Obama's critics have plenty of black friends,.. and those black friends hate Obama too,...

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