The 1st amendment may only protect us from the government, but there is nothing stopping us from taking away immunity from "platforms" that are actually acting

The 1st amendment may only protect us from the government, but there is nothing stopping us from taking away immunity from "platforms" that are actually acting as publishers. If a platform wants the liability protections for being a platform, then we can force them to not act like a publisher, or we can take away those platform protections.