Oddly enough, here Satan pronounces the Name of Jesus: Dante's devils would never have dared to, in fact they always used periphrases when they had to mention him.
Identifying non-Christian gods with devils is a stand dating back to the Tanakh / Jewish Bible (ofter improperly referred to as Old Testament), then developed by St. Paul and the Church Fathers, all the way up to Milton. This often led to including fairies, elves, etc., in the same hellish field. Only - in practice - with JRR Tolkien and CS Lewis would traditional Christian thinkers start to see the fantasy world as something neither angelical nor devilish, and basically positive.
It also dates back to the Tanakh to envision the gathering of all peoples around the true God, but in this case Tasso, with an implicit prophecy, also refers to the newly discovered peoples of America.