There appear to be a variety of reasons that include disagreement with his views, policies, ideas, a need by some for a scapegoat, personal bias and racism. Let's not forget it is common for some people to tear others down and this is possibly a factor. The office of the President has been disrespected more than I saw with Bush or Clinton and I find this sad because I was raised with the belief that is something to be respected no matter what. Perhaps his treatment stems from a general lack of respect for others that plagues our nation?
I have had people say, we must take back our/this country and when I ask from whom or what, they ALWAYS refuse to answer. That silence speaks volumes. President Obama has made minor and major mistakes like other Presidents. The current term will be over in the not too distant future and the "haters" have already started in on Hillary to a more insulting level than the white male Presidents have been held and she has not even said whether she will run.