That is Luther's presumption. It was never Catholic teaching. He presumes that man is totally corrupt because Luther was unable to make the distinction between the natural and supernatural gifts given by God to man.
So the seal merely puts us in position to receive infused grace to overcome our beastliness.
Baptism does a lot more than that. It makes us adopted Sons of the Father in heaven, sons with an inheritance that is freely held out to us.
Regards