You're asking moderators to a spend a large amount of their free time moderating discussions in which people are highly unlikely to change their minds on the topic. When we did previously allow these, the political threads were often threads that required the most moderation due to repeated rules violations. These threads often got very heated and it at times carried over to non-political threads. We only have a certain amount of time our moderators can voluntarily offer to the site and I'm not going to ask them to spend a good chunk of that time moderating topics that has nothing to do with the primary focus of this site. Primarily for that reason, political and religion-based threads have been moved off site for numerous years and we're not going back on that decision. Our stance on this has been very clear since it was implemented: no political or religion-based threads on this site.
Also see the stickied thread
in the Non-Baseball chatter forum on this very topic.