Martin Sheen, 75, is so proud of his 50-year-old son for announcing to the world on Monday that he's been battling with the debilitating virus for four years as he knew it was the "most difficult thing" he has had to do.
Speaking at the annual CME Group's Global Financial Leadership Conference yesterday, he said: "He had been leading up to this sort of story for several months, and we kept encouraging him to do it. He kept backing away and backing away because it was like going to his own execution, I guess.
"This morning, as I watched him alone, reveal his deepest, darkest secret, I couldn't believe the level of courage I was witnessing, and that it was my son.
"I left him a message, and I said that if I had that much courage, I would change the world."
The actor then asked the audience to view HIV no differently to an illness like cancer or substance abuse.
He explained: "I just want to encourage all of you that have children, spouses, aunts, uncles, clients, that are involved in any form of addiction to realise that it's a disease and if it they had cancer, you wouldn't think of them any differently.
"But most importantly, people, and I speak from my own personal experience, most people who become addicted are looking for a transcendent experience."
Martin is now hopeful the 'Two and a Half Men' star will be able to live the remainder of his life positively and freely.
He added: "I hope that this day is the first day of the rest of Charlie's life as a free man."