How were the Galatian churches being perverted?
The Galatian churches were being perverted by troublemakers who came in and told them they had to keep the Mosaic Law as well. This twisted the truth off-center, turning grace into another gospel, which is not another, and misleading people away from the grace of Christ.
Les explains that Paul recognized the Galatian churches were being perverted by someone coming in and telling them they had to also keep the Mosaic Law. He defines perversion not merely as something down in the gutter, but as anything that twists the truth far enough to be off-center and mislead people. Paul calls the added message another gospel, which is not another. He warns that even if an angel from heaven preached any other gospel, let him be accursed. Les notes Christianity has been bombarded with perversions since higher criticism began, and he shudders to think of the end of anyone who takes this gospel and perverts it.