Liberalism, progressivism, and leftism are not synonyms. In a Venn diagram there may be some overlap, but they are still very distinct.
Liberalism and leftism are “absolutes” while progressivism is a relative. In all cases, these concepts are about the rejection of control and subjugation. If you wander into a left-leaning space and find yourself downvoted, it’s not because of “herd behavior” but because you said something wildly unpopular (e.g. authoritarian apologetics).
Whether you think something is “plausible” is beside the point. If it is unfair, inequitable, or otherwise supports, advocates, excuses, or leads to “some being more equal than others” then leftists will rake you over the coals.
One more thing to remember: leftists are so used to being misrepresented, lied about, vilified, and trolled by the right (including liberals) that there is very little patience for anyone that stumbles in and spouts any manner of right-wing rhetoric, because it’s almost NEVER someone trying to engage in good faith.
So ask yourself this: WHY is what you’re saying unpopular?
If you are willing to swallow your pride and challenge yourself, most leftists will be happy to discuss just about any topic… if you are able to build the trust that you’re exploring a topic in good faith. Asking challenging questions is a good approach; in lieu of making statements, always ask questions. Everybody loves answering questions. Challenging others leads to conflict (and downvotes), but challenging yourself leads to enlightenment.