"Why is it that subjects like this can't be discussed without nasty accusations and name calling?"
My theory is two-fold.  First is the Dunning-Kruger effect in regards to politics.  Because everyone is affected by politics from the local to the state to the national levels as well as in most work places people tend to overestimate their knowledge and understanding of politics.  Which leads to the second which is partisanship.  This tends to be a nasty blend of confirmation bias, emotion driven knee-jerk reactionism and us-versus-them tribalism.  It leaves little room for reasonable disagreement in one's mindspace.