Steve didn’t murder Wakandans
I have seen posts going around about Steve being responsible for the death of Wakandans, that he sacrificed them because he doesn’t care about them, and that he cares more about a “MacBook with a cape”.
First of all, Vision is a sentient being, not just a machine. He is able to feel pain, happiness, sadness, anger, and he is able to die. He is able to fear death. He is able to love deeply, and grief when he loses it. He is able to make mistakes, to let his emotions cloud his judgement.
Though it’s funny to compare him to a toaster or a MacBook, in this context he is another life that can’t be given up without consideration.
Steve never asked T’Challa to fight, the King saw himself that it was necessary, and participated in it. Steve doesn't ask for anything but to find a solution for Vision so they don’t have to force Wanda to take the life of the only loved one she has left. T'Challa takes initiative, because he knows what's supposed to be done.
No one wants a war, Steve the least of all. He knows the destructive chaos of war, and though he was made for it, he always considers what they lost and the casualties (”They told me we won. They didn’t tell me what we lost.” “I'm not leaving this rock with one civilian on it.” “What about the others? Are you planning a rescue mission?”).
To say he “doesn’t care about Wakandan warriors” plainly isn’t true, also because he stood on the very front line of the battle. He was the first to advance into battle, and ready to fight for the universe. Also, in Endgame, we saw him stand up against Thanos’ entire army all on his own. One man against an entire army.
If T’Challa had refused to have Wakanda fight, Steve would have stepped up and done it on his own.
It’s also very clear: Team Earth doesn’t have space ships. They don't have the means needed to get to another planet, and of all the places in the world, Wakanda simply is the safest one. Any other place in the world would have ensured the death of many more people. Of innocent bystanders. There was nowhere to go but Wakanda. Tony could take over the Q-Ship and so steer it away from Earth, taking the fight somewhere else, but Steve did not have that option.
Even if they destroyed Vision, Thanos will come, and they had the choice to either fight against him in a city with civilians, or in a battle-hardened country with the best tech and warriors of the world.
Thanos started a war, and Wakanda decided that they would be one of the people to fight it.
It’s important to remember that the Black Order/Children of Thanos had already advanced onto Earth. They thrashed New York City with Tony, Stephen, Bruce and Wong, as did they attack Wanda and Vision. They already damaged the Earth, and we know they sought nothing but blood and death.
They were after the Mind Stone, which is in Vision’s head. It took them quite a while to get it, as Wanda managed to fend them off, and Natasha than fatally injured one of the two who attacked, causing them to retreat. They came back later, however, because they still did not have what they wanted. At this time, during the attack in Wakanda, Tony and Stephen are with the Guardians fighting Thanos on Titan.
The Children of Thanos would be coming anyway. They want Vision, or more specifically: the Mind Stone. They want it no matter what, it’s what they were coming for, and it’s their mission. Even when the Mind Stone would be destroyed, they don’t know that. Proxima Midnight wanted revenge on Natasha for her fallen sibling, and the Battle of Wakanda was the way to get that done as well.
Then: not only were we shown that it takes immense power from Wanda to actually break the stone (which came from a lot of emotion and last-minute adrenaline, and that she would have to be ready for), we also saw that that didn't stop Thanos.
You see, the moment Thanos gained the Time Stone from Doctor Strange, he had basically already won. He has five stones, of which one can repair/restore the others. Thanos was coming for Vision, whether Wanda would have destroyed the Stone or not, because Vision is Thanos’ key to getting the Mind Stone. Having the Time Stone allows him to simply rewind Vision and get the Stone, even when it’s gone already.
So it wouldn’t have mattered if Wanda had killed Vision or not.
I also think there is a nice parallel shown between Wanda and Stephen regarding the Stone they try to keep out of Thanos’ hands:
Stephen made it very clear from the start to Tony and Peter: “I won’t hesitate to let either of you die.” He said he is willing to let Thanos take their life if it means protecting the Stone, but when Tony is on death’s door, and Thanos threatens to kill him, Stephen trades the Stone for Tony’s life.
Wanda does the exact opposite. She refuses to have Vision die, and seeks for another way. When Thanos comes, and he’s headed for Vision, she, in contrast to Stephen, kills Vision for the sake of the Universe.
We were shown directly after that, no matter what Wanda would have done, Thanos already had the power to undo it. Her killing Vision was a meaningless sacrifice, because Thanos had obtained the Time Stone and could have taken the Mind Stone back whenever he wanted.
So even if Steve would have let Wanda kill “The MacBook with a cape” that wouldn’t have stopped the Black Order from coming to Earth to try and get to Vision. They needed him and his body anyway, with or without the Stone still intact, because they had the power to get it back.
Just like Stephen is not at fault for letting Tony live, Steve is not at fault for letting Vision live.
From the moment Stephen said there was only one way they would win, we knew that Thanos had to win first. So that meant that it didn’t matter what Wanda or Steve did at that point, because Thanos would have won anyway.
TLDR: Steve didn’t ‘kill’ any Wakandans, killing Vision would have solved nothing, Vision is a sentient being.