It's much easier to shut down an issuer than an exchange, which can stay mostly hidden.
Not a very good argument. The thing about a blockchain based system is that it literally cannot be shut down. That means I can send shares to whoever I want, whenever I want, without anyones permission.
I can see you making the same arguments you are making now against torrents and bitcoin as they share the same concept of decentralizing and universalizing the transfer of information.