The vehemence with which Paul denounces those who teach another Gospel (literally he says, ‘Let them be damned’) has bothered some, but this shows how little the Gospel of God’s grace is understood and appreciated. The word translated “eternally condemned” (anathema) is related to the Hebrew word, herem and is used of that which is devoted to God, usually for destruction. In Spiritual terms it means damnation. He is universal in his judgment. His words include “anybody” who should so teach (vs. 9). How can it be otherwise? If the Gospel Paul preaches is true, then both the glory of Jesus Christ and the salvation of men are at stake. If men can be saved by works, Christ has died in vain (Gal 2:21), and the cross is emptied of meaning. If men are taught a false Gospel, they are being led from the one thing that can save them and are being turned to destruction (cf. Matt 18:6).
Listen and identify any false teachers that you may be reading or listening to, repent and destroy the accursed thing!