Well for better or worse, our freedom of speech only limits government interference. You and I and every other private citizen is free to say, and to not say, anything they like within an extremely broad range. While private companies may have an ethical requirement to avoid censorship, they don't have a legal one. No matter how big their datacenters, no matter how large their audience, you don't have the fundamental right to force them to rebroadcast your message if they do not wish to. You may dislike or even be disgusted by their decisions, but remember that anyone who has the power to limit Google's freedom has the power to limit yours.