That person may or may not be s lost cause but in that particular forum, Linus has all the authority he needs. He might have made an antivaxxer an even stauncher antivaxxer but the message is received by hundreds of others. I absolutely agree that this tone isn’t how you persuade someone. It’s not how you’d talk in private. But that’s not what happens here. This is hopefully a net positive despite not persuading the poster he replied to.