Manifest the destiny

I disagree with the concept of manifest destiny becauase the americans came in and just took the land from the indians, but they didn't force them off they came in and just strolled in on them. I think they should of warned the native americans that they were going to come on their land insted of forcing themselves on the native americans. They even brought measels with them which isn't a good way to welcome yourselves in even if your not trying to hurt someone.