Because? Oh, right. Because you want to punish entities that you disfavor regardless of whether it violates what you claim to be your principled stance in favor of free speech and against European-style regulation of speech via those same platforms.
Europe criminalizes speech. "Criminalizing", in case you didn't know, means that a prosecutor can put you in jail for saying or publishing things that the government doesn't like.
I'm saying that private publishers in the US should lose their protection from civil liability when they exercise editorial control based on political views. Civil lawsuits require actual damages, require a private party to initiate, and don't result in jail time.
Ask a competent lawyer to explain the difference to you if that is still too difficult for you to follow.
And those protections are a special exemption from civil liability; since free speech is already guaranteed by the 1A, these special protections obviously don't protect free speech; what they protect is the ability of companies like Google to grow very, very big and not worry about certain lawsuits.