I saw 300 last weekend and it really upset me, though I wasn't quite sure why. I liked the movie pretty much in its entirety except for the adultery on the part of the queen. It seemed so terrible to me that she has sex with a fellow who holds out a vague hope to her. I've spent the last few days pondering why she might do that and why I had such a bad reaction to it.
I've come to this conclusion: she was in more desperate straits that I had realized at first. Her husband and king had marched to his death and she was the sole person who could save him from that death. Everything was up to her. The trusted advisor who was on her side had told her that if she was to have any success whatsoever she would need to have the traitor dude on her side, so when he offers his aid in trade for her sex the overwhelming hope of possibly saving her husband must have clouded her better judgment. As a viewer I could not believe that she actually hoped to have the traitor's aid, but her stoic outlook kept a great deal of her emotional affects at bay. The fact that she does sleep with the traitor shows how much pressure she was under.
:-) At least that is my euphemistic view of things... I still don't think it needed to happen that way, but it did show how dire straits were. One can argue for democracy and freedom as her main motivators but I don't see them that way. I see family as the real end behind those rationalizations.