It’s okay and expected for a private news outlet to publish slanted stories. However, Twitter is a privately-owned public chat venue, just like a southern lunch counter. The Supreme Court has ruled that it is illegal for such venues to discriminate on the basis of race because they speak as governments, on behalf of the entire community.
That’s illegal. However, when it comes to speech discrimination, that’s the purview of the Constitution. It’s unconstitutional for a privately-held public venue to discriminate against speech which the owner disagrees with. The owner is speaking as a government, on behalf the entire community.
And until Musk acquired Twitter it was taking direction from the US Government (or at least Government employees and agencies).
This is illegal from a bit of information I have been reading.