FB is engaging in massive censorship of information they don't wish you to see. Here's an example:
https://www.powerlineblog.com/archives/2020/11/facebook-fact-checks-me.php
The powers that be in social media know what's best for you and will actively filter out the "disinformation" (i.e., the information that does not align with the narrative they're telling you). Orwellian to say the least.
Parler won't filter out information, and thus they operate as a bulletin board, where users post information. FB, Twitter, etc. operate as publishers, as they review content and selectively permit "allowed" content to be posted. Under Section 230 of the communications act, that puts them into a category where they become liable for such content. In the past, they claimed freedom from liability, as they argued they were just the bulletin board. They've crossed the Rubicon.