Thanks for this. The biggest thing I think I’d challenge here is the perhaps unstated premise that U.S. political parties are monolithic or even have mechanisms for correcting themselves, e.g. your comments about the DNC. Party institutions face insider / outsider challenges and the people who are in charge of given party institutions are constantly making and remaking them. In practice, U.S. political parties tend to develop alongside presidential campaigns and other individual candidacies, though that can also change rapidly.
I also do think a lot of people are persuadable, but they’re usually not the ones who show up to a debate. I greatly value work I’ve done with students, in part, because it’s so great to talk to people whose minds are open and who are interested in what the different arguments are around public policy issues. By contrast, I think people who are professionally involved in politics tend to engage in arguments based on what’s acceptable to their coalition and what secures them an advantage, be that attention, money or power. A lot of political communication is about convincing people who agree with you to become more involved in politics, not convincing people who disagree with you to agree with you.
Practically speaking, I can enter into a coalition with someone who disagrees with me about fundamentals, but not a specific policy. For instance, climate advocates have entered coalitions with libertarians to secure rights for rooftop solar owners. Climate advocates get more clean energy, libertarians get more property rights on their rooftops, but if you tried to extend that agreement to requirements for how utilities produce electricity, the libertarians would drop out. If you tried to extend that argument to fundamental rights that future generations have for a sustainable climate, most libertarians would reject that argument outright.
So I see “both sides” arguments as useful sometimes, but it depends on what purpose one is using them for. If one is using them to opt out of politics or feel above “both sides” then it’s not an argument that has utility, usually!