Why didn't Obi-Wan tell the truth to Anakin on Mustafar?

Question

In Star Wars Episode III, before the battle on Mustafar, why didn't Obi-Wan admit to Anakin that it was his idea to hide in Padmé's ship to find him? His hate towards her would at least be forgiven, since Obi-Wan had no idea how the confrontation with Anakin would start or if Padmé died.

Answer 1

A part from the script:

Padmé: Anakin, I was so worried about you! Obi-Wan... told me terrible things!

Anakin Skywalker: What things?

Padmé: He said... you turned to the Dark Side. That you... killed Younglings!

Anakin Skywalker: Obi-Wan is trying to turn you against me.

Padmé: He cares about us.

Anakin Skywalker: Us?

Padmé: He knows. He wants to help you. Anakin, all I want is your love.

Anakin Skywalker: Love won't save you, Padme. Only my new powers can do that!

Padmé: But at what cost? You're a good person, don't do this!

Anakin Skywalker: I won't lose you the way I lost my mother. I am becoming more powerful than any Jedi has ever dreamed of, and I'm doing it for you. To protect you.

Padmé: Come away with me. Help me raise our child far away. Leave everything else behind while we still can!

Anakin Skywalker: No. Don't you see? We don't have to run away anymore! We no longer have to hide our love for each other. I am more powerful than the Chancellor, I... I can overthrow him! And together, you and I can rule the galaxy! We can make things the way we want them to be!

Padmé: I don't believe what I'm hearing! Obi-Wan was right... you've changed! You have turned to the dark side! You're not Anakin anymore!

Anakin Skywalker: [with a growing angry look and voice] I don't want to hear any more about Obi-Wan. The Jedi turned against me. Don't you turn against me!

Padmé: [crying] Anakin, you're breaking my heart! You're going down a path I cannot follow!

Anakin Skywalker: Because of Obi-Wan?

Padmé: Because of what you've done... what you plan to do! Stop! Stop now... come back... I love you! [Anakin looks beside Padme and sees Obi-Wan standing at the ship's exit overhearing them]

Anakin Skywalker:[enraged and paranoid] Liar! You're with him! You brought him here to kill me!

the part of enraged and paranoid defines it all I guess.

Obi-Wan Kenobi: You have allowed this dark lord to twist your mind, until now, until now you've become the very thing you swore to destroy.

Anakin Skywalker: Don't lecture me, Obi-Wan! I see through the lies of the Jedi. I do not fear the dark side as you do. I have brought peace, freedom, justice, and security to my new Empire.

Obi-Wan Kenobi: Your new Empire?

Anakin Skywalker: Don't make me kill you.

Obi-Wan Kenobi: Anakin, my allegiance is to the Republic, to democracy.

Anakin Skywalker: If you're not with me, then you're my enemy.

Obi-Wan Kenobi: [realizing that Anakin is consumed by evil and there's no reasoning with him anymore] Only a Sith deals in absolutes.

[draws his lightsaber]

Obi-Wan Kenobi: I will do what I must.

Anakin Skywalker: You will try.

[draws his lightsaber and confronts Obi-Wan]

IMHO, I think because Palpatine totally turned him to the Dark Side, clouded his mind, always took his side etc.

Anakin feels betrayed by Obiwan since he was under his control. Being "freed" by Palpatine makes him hate Obiwan more and more. Till the point that he no longer can seperate Good from Wrong and defines it anew. This resulting in Force Choking Padme and ultimately a whole breathing apparatus upon losing some limbs.

EDIT: Also, maybe a part of shame/sorrow/guilt took place in his mind, fueling his hatred towards anything that would take Padme away from him. As did the Jedi code. (Thy shalt not breed - Jedi)

Thus resulting in him being so enraged and unreasonable that he won't accept anything Obiwan would have told him. I assume here that Obiwan sees/feels this and doesn't say anything to Anakin untill Anakin starts Force-Choking Padme.

Answer 2

After their confrontation, when Obi-Wan and Bail Organa bring Amidala to the secret asteroid base Polis Massa, the medical droid says:

Medically, she is completely healthy. For reasons we can't explain, we are losing her.

This implies that Padme died not because of her wounds inflicted by Anakin's force-choke, but rather of a "broken heart" so to speak. Obi-Wan or Amidala herself were hardly at fault here, as Anakin's own confirmation of his fall to the dark side is what ensured Padme's demise. Whatever Obi-Wan could say when he confronted Anakin wouldn't have mattered. At that point Anakin had already turned to the dark side, and saw Obi-Wan and the Jedi as his enemies that kept him from "saving" Padme.

Answer 3

Padme didn't die of a broken heart. Her life was taken from her by Palpatine to save Vader. Palpatine was the one who was creating those nightmares that Anakin was seeing. Yoda warned him of this, Anakin never killed her, when he wakes up from his procedure he says that he felt her alive before his fight with his master. Sidious was able to create and take away life, he just tricked Anakin into thinking that it was pivotal to Padme's survival. Yoda warned Anakin of fearing loss as that is a path to the dark side. Anakin's vision were only true because he made them true, if Mace kills Sidious, Padme lives, she was always going to live.