There is a difference between a frontier which is habitable but inhabited and a frontier which is not inhabitable without artificial tools. Settling Mars is not like settling the prairie. Its more like settling the bottom of the ocean and we have not managed to do it even though its just 7 miles away. Asking people to go as settlers at this point is just murder. If we were to send professionals to start a terraforming and then send Settlers in 100-200 years once the terraforming has started to take effect it would make sense. Sending settlers without terraforming is just not economically feasible. We would have to evolve a separate species who could live in artificial environments forever.