"No rule is better than bad rule" may be closer to my argument, though it dips further into anarchy than I'd like. People are welcome to try as they like, but governments aren't people. If Facebook wanted to try some system like Parler had I wouldn't protest against it, but the UK government mandating it would have far more reach and requires more consideration as a result.

That's true. On the other hand, "The pros and cons of such a law are so mixed as to make a good one impossible," is a good reason not to make such a law. I think many of us see any law that could be described as "banning anonymous accounts" as being written with too broad a nib to be useful.