The answer is: It is among the first American written works to promote tolerance.
The 'savages' is the term used by people from united states for the native Americans. At that time, not many political leaders dare to defend the native Americans since due to the fear of losing support from the people.
But Franklin at that time is the first one who dare to challenge this terms. He stated that the only reason why we call them savages is because their way of living is different from us. Otherwise both native Americans and the white colonists are equal human being.