I'm not sure insisting on the free speech analogy is the correct approach to be honest. Speech is general in content: I can arrange words in such a way so as to express whatever meaning I want. Bitcoin is, in principle, not general in the kinds of transactions that are to be ideally allowed on its network. Let's imagine for a moment a world where Bitcoin only allows P2WPKH outputs and absolutely nothing else. Let's imagine this is agreed upon by all holders such that all other outputs are transferred to P2WPKH ones. Would this be problematic for Bitcoin as money?