Freedom of speech is a nice concept, and one worth fighting for. It's not something you can assume you have a legal right to on the internet, especially when you consider all the different countries' legal systems involved (my own country offers pretty patchy support) Sop when I say "right" here I just mean in the non-legally binding moral imperative sense.
But even when we consider the principle, what it means is that you have the right not to suffer legal consequences for expressing an opinion, and the right to have public spaces in which you can express yourself.
It does not mean you have the right to avoid social repercussions. If it did, wouldn't you complaining about the people complaining about you be a violation of their right to "free speech"?
Secondly, just because something is publicly visible doesn't make it a "public space". If a private individual or organisation is in charge of a space (and this is true of pretty much everywhere on the internet) then they have the right to completely control what is said there, and that includes deleting content and banning contributors. Which is not to say that this isn't sometimes a bad thing for them to do if they are inconsistent or overly harsh, but they still have that right to dictate both the general nature and specifics of what is and is not said.
If you want to say something they don't like, say it somewhere else.
On the other side: if you are in charge of a space (the comments to your blog, say), while in principle you have the right to run it how you like people will be justifiably annoyed if you act inconsistently or (in their opinion) overly harshly.
For further discussion on the specific issues involved with blog comments, you might like to read my post
POLL: When is it ok to edit a blog post?.
This post was written as part of my
General principles of internet communication.