I agree with you. Apologies; I was unclear. Scenario in my head: actor (a) spreads hate speech, actor (b) goes and kills someone named as the hated party by (a)

I agree with you. Apologies; I was unclear. Scenario in my head: actor (a) spreads hate speech, actor (b) goes and kills someone named as the hated party by (a). Unless (a) directly incited (b) (via the boundary test you cited), (a) isn't legally guilty of anything. But if the law discovers (b) heard (a) and acted because they believed (a)'s rhetoric, (b)'s crime rises past just violent crime to hate crime (because their reason to commit violence was a hate-crime motivation).