Banning ordinary Russians from using American services would remove the last place where Russians can express their opinions freely, playing into Putin's hands.
Why can’t they spin up a blog? Also, as an American, I don’t think those FAANG places are a safe space for “expressing opinions freely”. The boys (bots) will come.
An independent blog is easily banned. In fact, most of them are already. Platforms like Facebook host millions of pages and use https so it's not possible to ban individual pages, only the whole thing. And they've been hesitant to ban whole social networks because of possible discontent