The reasons they hate him are many (They=Media and establishment), but the main reason is that they cannot control him. The reason they cannot control him is that they did not make him, or create him. The establishment and the Media have always "created" politicians and Presidents. They were not real, they were created out of thin air.
It has always been, what they have giveth they can taketh away. The problem for "them" is, they did not give us Donald Trump like they did the Bushes and the Clintons and that Snake Obama.
He is real and not an establishment/Media "creation" and they have Zero control over him. Without control, or him being their puppet, they cannot stop him.
God Bless Donald J Trump.
Give a man a fish and he eats for a day. Give a man a welfare check, a forty ounce malt liquor, a crack pipe, an Obama phone, free health insurance. and some Air Jordan's and he votes Democrat for a lifetime.
