Its a 1st Amendment issue. That professor has (and should have) every right to speak their mind, just as every student has the right to refute it. This should be the stated purpose of the university - to give everyone differing opinions on the issues - and allow them to make up their own minds. Unless this is some rinky-dink college, there should be other professors from which to choose if this one is too left-wing for your tastes.
The real question is why extremists (both sides) are being hired in the first place. Those folks aren't real teachers, they are indoctrinaters who couldn't get anyone else to listen to their BS so they are "professing" it to an audience without the experience, ability, or willingness to stand up to them. But usually they are in departments that have little interaction with the mainstream student. Instead, they spew their drivel and hatred to just a handful of misfits and mental midgets who will soon get a real kick in the pants when they graduate with thousands of dollars of debt and no job prospects. They'll join in on the protests, believing the conspiracy theories about "the man" and "the establishment" and then, after several years, come to the conclusion they were simply sold a bill of goods that was nothing but emptiness.
Choose your university wisely. This was a much bigger problem before the internet and social media. Today, you don't know what your professors and university stands for and believes in then that is on you.