The question is also which relay. Anything hosted in the EU, Russian, or Australia can get easily shut down by the hosting company, for instance, even if the material is not actually illegal.
So how do we set up a relay farm in the middle of the ocean where it isn't under the thumb of any government?
If relays were built to be small, fast and efficient, using a small, fast, and efficient language, and incorporated a DNS alternative, a million+ relays could be run on SBCs. Combined with a desktop application using @jb55's nostrdb, so that 100% uptime isn’t required, it would be damn near unstoppable.