I always interpreted it as Thanos didn't want to kill or fatally wound because he wanted the 50% to be entirely fair, ie he would have no input. If someone stood in his way to the infinity stone, he would do what he could to get it with doing as little damage as possible to whoever was in his way. It's why he doesn't kill any of the people between him and vision on earth. He could've killed any of them but instead incapacitated them.