First, Non Av is far from a "left wing" echo chamber. There's too much hyperpartisan posting on both sides. I can absolutely assure you that for every vocal left wing poster, I can name the right wing equivalent poster.
I don't need you to assure me or show me anything. I need to you moderate the site in a consistent manner. What side of the fence you or I are on is irrelevant. The point remains, you allow 18 different political topics on the first page of Non-Av, yet a thread about the Golden Gate Bridge must be deleted merged into another thread.
Second, a political mega thread would be extremely difficult for us to moderate. I would even go so far as to say it would be borderline impossible, it would make us miserable, and we would quickly abandon the idea. We requested the developers create a politics forum a few years ago to at least separate the chaos, but it never happened. That's unfortunately outside of our control.
No more difficult than the airline and geographic topics in Civ-Av. As for making moderators miserable, that's ultimately irrelevant as it's a volunteer position and your user experience is second to the members.
To be completely honest, we (the moderators) would all prefer to ban political discussion outright. However, users want to discuss politics, so we allow it to the extent possible by limiting it to Non Av. There's nothing for us to "clean up" on the basis that you aren't a fan of the topics on the first page, and we are treating threads equally regardless of content. We aren't going to determine which threads should and shouldn't exist unless it runs afoul of the rules, and it's not our raison d'être to create threads or posts to balance out the forum. If you want to discuss something else, then it's on you to take that initiative.
Do you actually believe yourself when you say you treat threads equally and you don't arbitrarily decide which threads get to exist without proper communication?
The fact you took an immediate defensive stance over a suggestion to review the way political threads pollute Non-Av is strange. It shows a lack of understanding on how to moderate a website in a consistent manner and without bias. If you're not up to moderating in such a way, which it sounds like you're not based on the other threads in Site Related, perhaps it's time to hang up the keys. Until then, I suggest you learn to take constructive feedback with an open mind.