No discerning is not judging it is to be aware.
Do you think to rend ones word or to turn words against another is a godly thing?
Do you think mocking and ridiculing is someone who is walking with the Lord?
If someone pokes you in the eye on purpose you know it did not come from a place of reverence.
Reading the hearts and minds of others is NOT discernment, much as one would wish it to be.
I think that one should consider the beam in one's own eye before perceiving the mote in a brother FReeper's eye, and to me that "beam" includes "discerning" someone else's "sin" and pronouncing judgement upon it by way of naming someone "natural man". Matthew 7:3
Especially given the definitions you posted of what a "natural man" is.