Except this is disingenuous. There are political discussions found here, but one side is generally downvoted.
"The rule is already broken in one direction, so it should be right to break it in another" isn't a helpful take IMO.
You said that you saw one side being downvoted. I took that as meaning you thought it should be left alone like the other side is, when IMO that is not the solution. If both are off-topic (which they usually are, by my reading of the guidelines) both should be down-voted. The fix for the imbalance is not to encourage more but from other angles, it is to enforce the desired topic limits evenly.
(using the word "side" above may be ill-advised on my part, I know most matters are far more complex than a binary this-side-and-that-side, but better wording did not spring to mind)
You can, for example, debate pro-vs-anti nuclear power without necessarily getting downvoted. You can't post straight up climate change denial.
You can argue that the stackexchange moderator fiasco was incredibly badly handled. You can't post straight up homophobia.
Please don't post ideological flamebait to HN or take threads further into flamewar.
There is room for reasoned debate but many are incapable of it, especially on an internet forum.