So, I don't understand how this is fair...do you?

When the Pilgrims came to the New World, they wanted religious freedom, correct? But then they tried to convert the Native Americans. Why? They saw them, eventually as demons in human form. Then they began to kill them. Why couldn't they have just practiced what they preached and let the Native Americans have their own religious freedom? Why can't we, as Christians, do that today with other people and cultures?