Lexa's alliance was with the 12 clans PLUS the Sky people. Her betrayal means she cannot be trusted. Her promise that the end of the tyranny of the MM was now, that there would be Blood must get Blood was not kept.

Ok, somebody else gets it. Thank you. For most of us living in the west, the warrior idea of the honor of dying in battle seems harsh and it may seem enlightened to avoid war, but for those living in survival mode, the glory of battle is sometimes the only thing you can offer your warriors.
Betrayal is not something a…

"The Commander can't just do what she likes because maintaining these relationships matter."

Oh I'm sure they'd have no problem with killing and destroying the Sky People in battle, but betrayal of someone in an alliance THEY are a part of is different. If it were me, I'd wonder when my clan would be expendable. The sky people had disabled the power, removed the poison, and found a way to return their people…

Imagining…I wonder what kind of discussion Lexa had regarding the deal:
MM: I've been authorized to offer you a deal. All we need is the Sky people and we can live on the ground. We will no longer have need of your people.
Lexa: But my people are warriors who find glory in battle. Peace is something the sky people…

Oooooh, Clarke revealing Lexa's deceit would be wicked :) BUT that would make Clarke cold blooded, something Lexa was trying to teach Clarke huh?. Lol.

Not explicit; but for most warrior class people, honor is everything. Do you know of any warrior that doesn't use "honor" as a reason for killing? Pride, sacrifice, honor they all go hand in hand for all military base groups. Betrayal for expediency sake is hardly honorable, is it?

Again, the very core of ANY alliance is trust. If she could betray one of those in the alliance, why would any of the leaders of the other tribes believe she wouldn't betray their tribe?

Until that moment, while I disagreed with some of the warrior class mentality, I understood that they were in survival mode. But betrayal is old as time. The alliance, not just with the sky people, but the other tree people tribes, THAT was pragmatic and visionary: uniting to win.

EXACTLY!! Her betrayal was neither pragmatic nor visionary. Betrayal is as old as time.

Ok, let's take the emotion out of Lexa's decision to betray the Sky people. If you were a leader of one of the tribes, would you trust someone who vowed that the tyranny of the mountain people would end today, that "Blood must be given Blood" and all that warrior inspiring speeches, at the very point of victory, tell…

As for caring about avenging her people, when she called for "blood must have blood" and "the domination of our people ends now", yeah I thought her words meant something. But you've all convinced me that she lies when it suits her and her people do not have the honor of warriors.

Exactly, the sky and tree people attacked each other; the mountain people took and used the tree people. One meets the other in honorable battle, the other take and use. That is why Finn had to die because it was a massacre not a battle.

And again Lexa has told her people that the mountain people's domination ends TODAY. She told them the mountsin people would pay for the 200 who died. She has shown that she will betray an alliance and act without honor.

The rescue was Clarke's desire because of who she was and how she was raised. The mountain people was raised for Blood must have Blood. Again it goes against who the mountain people are: warriors with a simple sense of principles. The idea of trusting people who has terrorized your people for decades is not just…

Wait a minute, wasn't "Blood must have Blood" paid by the death of Finn? And wasn't the death of grounders due to their attacking the sky people? For warriors, defending themselves make sense, the massacre by Finn did not. So Clarke came as an equal to the "Blood must have Blood" victim of the mountain people who…

Lexa told the alliance that the domination of the mountain people ENDS TODAY; she sacrificed over 200 and demanded Blood for Blood, THIS was who her people was and something Clarke needed to get if there was going to be an alliance. If betrayal and compromise is a new kind of leader, it is a leader of another people…

Everyone INCLUDING the writers seem to forget that "Blood must have blood" . Where is the blood for all those who died at the hands of the mountain people? Lexa has gone against everything her people supposed to believe in. Compromise and betrayal isn't what warriors do.