Attachment is selfish, but not being attached can also come across as selfish. I am not attached to you, so I’m not going to go out of my way to help you. Selfish. If you look at it long enough, though, it becomes unselfish. I’m not attached, so I don’t mind that you’re upset at me, especially if it helps you become less attached to me.
The truth is like a lion. You don’t have to defend it. Let it loose. It will defend itself.