I don't think the bug is with Halsin at all. It's with Wyll and Karlach.
Halsin accepts that you killed the druids because they were in the wrong. What he does not accept is that you told the goblins where the grove was, because that means the goblins killed all the refugees. He can't accept that. The bug here is that Wyll and Karlach apparently don't notice that you got all those refugees killed.