Mars: To terraform or not to terraform?

Having read Both of Robert Zubrin’s books, I am now firmly on the “Colonize and Terraform Mars” side. Zubrin makes the argument that, when civilizations go static, they fall. Therefore, we need a challenge. i.e., settling Mars would be that challenge. Lack of labor on Mars (like America in colonial days) will result in the creation of labor-saving devices and other inventions that can be sold on planet Earth.

Plus, I think it would be really cool a couple hundred years down the line when Mars revolts and tries to leave the Earth Alliance…

What? Why are you looking at me like that?

First of all I don’t think we humans have the technology to do such a project anytime in the future, far off or not.
Secondly the martian soil is rather salty, finding a plant that will live there will be a bitch.
And last of all, Why did mars lose it’s heavier atmosphere in the first place? It doesn’t have enough gravity to hold an atmosphere needed by plants and us.