Everywhere. Just look for anything that goes against (even slightly) the leftist perspective, such as:
anything critical of trans people competing in sports - a lot of those policies are bigoted, but there are legitimate concerns
evidence that the economy is not as bad as people claim - e.g. cars aren’t more expensive today than they used to be, bottom of the market cars are about the same price as they were 20 years ago, after accounting for inflation (they’re actually a little cheaper in many cases, and have way more tech)
arguments criticizing Biden/Democrats
anything anti-socialist
And so on. The quality of the argument doesn’t matter, what matters is that it doesn’t fit the leftist agenda, so it gets downvoted like crazy.
Go ahead, try playing devil’s advocate sometime (and don’t say the equivalent of “I’m a leftist, but…”) and cite your sources and see how well your post does vs comments that ignore facts and spout common leftist rhetoric, the lower effort post will get more votes and yours will probably go negative.