Because the left tried to break into the capitol. Left are insane for wanting equal rights for lgbt people so everyone can just be happy. Left are insane for wanting to control gun use in the country which has had the 9th highest gun violence rate in the world. The left are insane for wanting to implement amber alert systems for mass shootings in the area.
It's true that the entire senate is mostly useless and acts in it's own interests (even some of the democrats), but the right's ideology of libertarianism lets them do even more bad things and not getting flac from their voters for it.