Locking up placard-wavers is stupid, but so is intentionally waving a placard with the name of a proscribed group, when just about any other message supporting the cause would be fine.

If you do a million pounds in criminal damage and attack a police officer with a sledgehammer, you can't just write it off as 'direct action', you deserve a tough jail sentence whatever the cause.

> proscribed group

If the government is legitimately evil for proscribing a group they should be able to deal with their constituents calling them out for it. Materially hindering a genocide is by all currently accepted human standards a good thing.