yes, alice has autonomy over who participates on conversations she started. bob is still free to have the same conversation, just not on alice's conversations or as replies to her.
i dont't think we're going to agree on why people generaly block others. you seem to see yourself as some sort of dissenter, or a truth-teller of some kind, but when you get blocked for interjecting into someone else's coversations it's just because no one asked you to be part of that conversation and now you lost your access privileges. this rejection probably fucks with your self-esteem more than it should but i'm no therapist so maybe go find one instead of annoying folks on the internet.