It appears you have given a perfect illustration of the comment you are replying to.
We can simultaneously see that partisan politics isn't completely rational and also observe that one side, for various reasons, is working that irrationality harder than the other.
My anecdotal evidence bears this out. Progressives tend to be far more intolerant of opposing viewpoints than conservatives.
https://www.washingtonexaminer.com/majority-of-democrats-at-...
Is the takeaway from this that holocaust deniers are more accepting people?
As another reply to you has shown, it's very easy to find specific differences and elevate them to an all-encompassing explanation, if that's how you decide you want to look at things.