Makes sense to me. No one wants to get burned at the social media stake. It feels no matter where you land on the political arena you're liable to get reamed by those who think your views are too strong or not strong enough.
Perhaps more bluntly, are you yourself a Nazi, a Communist, or happy with where the US is politically? If you're none of the above (as you likely aren't), then you must be able to see that moderate views can still be left or right-leaning.
Maybe the kindest reading of your comment is that the average person that's overly critical on Facebook only sees in black and white, left vs right. And if so, we completely agree :)