The parent poster never said their "side" was Democrat or Republican, only that it was Facebook's political agenda. Facebook's agenda is promoting the maximum amount of outrage so it can increase engagement. You can play all sides of the political spectrum to achieve that.
I didn't and I am not going to be coy about it, I am right of center of most issues. It really annoys me to see Facebook shut down the "truckers convoy" facebook organization even but at the same time never shut anything down relating to BLM as just a recent and obvious example. That said I don't want either shut down. I think these platforms should seek to emulating the free speech *principles* of the first amendment even if they aren't bound legally by them (today) where anything up to incitement of violence is unacceptable. Today its just a disaster where they ban/deboost people for political views that aren't left wing, banning "misinformation" that is actually true, and are funneling dark money into elections, and god knows what the hell they are doing with all the data.
All I recall was accusations by political parties from both sides.
Just because some content got popular amongst some cohort, it doesn't mean it was being pushed as an agenda. That is a problem any platform that depends on user activity to surface content will have, that you might see whatever the other side wants to share too.