That's why it'll be very important for relays to get "mirroring" functionality soon. This way, every relay can pull in content from other relays, so that you can subscribe to any relay and be confident you're getting most, if not all, of the posts from your follows. You won't need to rely on a few big popular relays.

If most of those relays, and the relays they subscribe to, block a certain user or type of content, then it's on those certain users to run their own relays to host it. The principle of free speech doesn't automatically mean someone is entitled to have their content shown to people who don't want to host/view it.