It is possible to disagree without being disagreeable.
There is always a rational point to bring, at least among rational persons. Persons who become completely irrational act out in ways that are intended to be absolutely inappropriate. This is merely the symptom of a far worse disorder than merely having a difference of opinion.
In the truly extreme cases, those who are utterly irrational will trey to block opinions, not because of their content, but who brought them. Hitler was infamous for saying, "We have no need of Jewish physics." With that he ordered all scientific papers written by the most brilliant men in germany destroyed in the infamous, "Burning of the books."
Hating another person enough to plunge an entire society into darkness, ignorance, and barbarian violence, is the mark of a true barbarian.
How, therefore, might we bring barbarians around so that they do not cost us all everything in the name of fascist hate?