Perhaps that was something of a policy decision - if people are at greater legal risk if someone is hurt, that can only tend * against * antisocial behaviour if anything … ? Though the most antisocial people aren’t exactly consulting and interpreting legal precedent, before acting … I recall a case from law school (I think it was an R v Brown … all the most messed-up cases seemed to be an R v Brown, for some reason …) where the Court determined that it was not possible for someone to consent to another party nailing the first party’s scrotum to the floor …