But we don't have a centralised ledger here and we value our freedom (or, at least, some of us do), which is why we call such projects altcoins. People can go and play with those if they like banning stuff.
You can also have a blockchain that prevents arbitrary data (aka spam) by design rather than by banning:
https://bitcointalk.org/index.php?topic=5437464.msg61782921#msg61782921