I've been reading a book, Death by Government, written by RJ Rummel, and it underscores your point.
The 'Young Turks' dehumanized the Armenians and brutally killed men, women, children, and old folks without any compunction.
The Khmer Rouge Commies in Cambodia did not blink any eyes in brutalizing fellow Cambodians who they had dehumanized for not being hardcore commies.
The Nazis dehumanized the Jews (and others).
The Soviet Commies dehumanized 'everyone' (even erstwhile supporters who they butchered to keep other people aniline).
The Chinese did similarly (not surprising since Mao's role model was Josef Stalin).
And so on.
Quite a depressing read - as this reveals the depravity in the heart of man (Jeremiah 17:9 The heart is deceitful above all things, and desperately wicked: who can know it? ).
Your comment is not an exaggeration - and a reminder that we all need to zealously guard ourselves from being infected with this noxious disease.
No matter how loathsome we find the progressive policies - we are to love our neighbors (even the progressive ones) as ourselves and remember that all people are made in the image of God. Oppose them (as we'd want to be opposed if we were pushing something wrong) - but never succumb to dehumanizing our opponents. Politics aren't the ultimate goal - Man's purpose is to give Glory to God.
“There are none so blind as those who will not see.”
Woe to those who call evil good and good evil, who put darkness for light and light for darkness, who put bitter for sweet and sweet for bitter.
I prayed around the election to receive help in removing the hate from my heart for Hillary and other liberals. We must oppose them at every turn, but hating and wishing ill on them just turns us into them and separates us from the Lord. It helped, but it continues to be a struggle.