Isn't that crazy?

It's not only denial, it is actively subscribing into the belief that the other side is wrong, and we must "get rid of them" in order to restore peace, harmony, the "good old days", regain wealth and abundance. If only, and if only MY SIDE wins and dominates over others that I "can have peace".

This kind of thinking is perhaps closer to during the 19th century, where there is a need to have power over others, whether it is other tribes, religions, countries. There's a term for this – Nazi.

We haven't changed much, at all. It's just a different flavor, through a different medium, dressed up in different clothing.