Oh that's easy.

The Polish government (like most authoritarian governments) wants sole control over who has censorship authority. [0][1][2]

Also: You're conflating "speech they don't like" with "policy violating conduct" which IS legally enforceable in most countries, including Poland.

As usual: Don't like it? Go somewhere else. Just not Parler, they couldn't host a piss up at a brewery.

[0] https://apnews.com/article/poland-courts-warsaw-2dece52da1fa...

[1] https://ipi.media/as-violence-escalates-in-poland-journalist...

[2] https://ipi.media/alerts/polish-journalist-arrested-while-co...