I almost said exactly the same thing you just did. I have absolutely no clue which "side" he's talking about.
"I think it's the party engaging in voter fraud [1] throughout the country, and the one that tried to impeach the president when someone from the other side won [2], and the one that literally fled the state so that the legislature didn't have quorum and couldn't pass legislation [3], even though they were a clear minority. Or the one that falsely accused a supreme court nominee of rape [4], in an unprecedented move. I could go on."
It's evident to me that people of all political bents in this country are extremely tribalistic, and none of the tribes count many saints among their numbers.
Citations added simply to highlight that I'm not pulling any of this out of thin air:
[1] https://www.heritage.org/voterfraud
[2] https://www.washingtonpost.com/graphics/2019/politics/impeac...
[3] https://www.npr.org/2011/02/17/133847336/wis-democratic-lawm...
[4] https://reason.com/2018/11/05/brett-kavanaugh-due-process-fa...
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.
This is hardcoded in us.