Because I am betraying allies. They pledged themselves to my cause when they were under no obligation to. Sure they could die facing the Reapers, but that is death at the hands of the enemy. That's the threat everyone faces.
Shepard choosing to shoot the tube, however, is Shepard deliberately choosing to destroy all synthetic life. This isn't sending them into a fight where they are likely to die. This isn't an omission of action. This is actively choosing to kill your allies. And not giving them a say in the matter.
People sometimes compare the choice to Virmire, but there are several major differences:
1) Scale. Virmire involves saving a single human life, and perhaps a small number of salarians. Wile the choice there sucks (or doesn't, if you don't care about those involved) it pales in comparison to the scope of an entire form of life. Not even a single species, but all species of a given type.
2) Choice. In the case of Virmire, both characters know the score, and are okay with laying down their life for the cause. In the case of Destroy, nobody knows the effect shooting the tube will trigger. While people might be willing to lay down their lives for a cause if asked, killing them with a bolt from the blue (or red in this case) without even letting them know why they are being killed strikes me as very cold.
3) Acceptance of responsibility: Virmire allows Shepard to apologize to the one being left behind or even claim to try to rescue both (which isn't really believed) and afterwards, has the chance to own up to the character's death afterwards. Frankly, I find joyous celebration after so many of your own allies have been annihilated to be quite the disturbing image. Perhaps understandable, given they were facing destruction just beforehand, but from my pov, it leaves me cold. Especially with the epilogue where the geth are essentially unpersoned.
Yeah, I know no ending should be perfect, acceptable losses, and whatever. But you know what? Those who die so you can live ought to be remembered and honored. I don't see that at the end of ME3. Nobody cares that a powerful ally fell saving Earth, even the whole galaxy. Edi gets her name on the memorial wall, whoopie! I fine remembrance for someone who had Shepard's back for two whole games. Loghain in DAO gets greater recognition.
But hey, at least he gets to volunteer to be archdemon bait.
You aren't 'betraying' your allies. You're sacrificing them for the cause. You have to sacrifice people for the greater good sometimes. If anything, there deaths should make the choice more meaningful, giving you full reign over what you're buying with their deaths. You aren't wasting them. You're spending them. That's something you should learn, instead of complaining about emotional distress at having to make a hard decision that weighs on your conscious. That's what leaders do. That's what all Soldiers do. If you can't understand that, then it means you're too weak to stand for something, to truly stand for it. You have to be willing to sacrifice what you love for the sake of what you both fight for.
It's not actively choosing to end synthetics, it's choosing to end the Reapers and acknowledging that the loss of synthetics is a necessary consequence for that goal. They don't need a say. Freewill is a bane as much as it is a boon. Do you really think I'd warn my allies I was sending them to their deaths if it meant buying me an advantage to win the war? Once more, it's not heroism or honor or goodness that motivates you. It's cowardice. You are a coward. You deserve no say over your fate, and no say or right to question the actions of others.
Scale is hardly of consequence here. You can temporarily end that entire domain of life, or you can accept the entire end of most forms of advanced sapient life. As I said, it's cowardice.
Emotional distress on your part. You do what you have to do, or you die. Frankly, according to your decisions, you deserve to fail miserably because you choose to hold onto some misplaced ideal of honor and compassion that will only end in even more suffering. So yeah, you're also a sadistic and evil wretch as well as a coward for choosing to bring suffering, misery, and terror all so you can feel ok with yourself because 'at least I didn't do anything mean to win and survive'.
Responsibility? Whose responsibility? This goes hand in hand with the last one. You don't need to apologize to people for sending them to death, even when they can live. Christ, you're as bad with David with the whole 'heroism' stick. Yes, there'd be joyous celebration, because they live. Because they get to continue and go on. You know the worst way to honor someone? To sit around and mope about it and how sad and disgusted you are. Instead of doing that, why don't you try honoring their memory by living life to the fullest and making their sacrifice meaningful? Why don't you enjoy the life you saved instead of mourning the life you killed? That makes you come across as pathetically narcissistic and self-centered. So you're a sadistic, self-centered coward. That's my summation right there of you and your emotional distress and 'bad feelings'.
You're certainly not honoring any body by complaining about how they're dead. So you're a hypocrite too. Instead of enjoying the life (the best possible honor to their memory), you choose to insult it by moping and whining about it.
That's just sad, and infinitely more evil than anything you complain about. You should strike that quote from your signature. You don't deserve to be called a hero. You're the worst villain of them all; the one who perpetuates evil in the name of false virtue.
As I said:
Are you so craven?