pernicious ways - The oldest manuscripts and Vulgate read, “licentiousness” (Jud 1:4). False doctrine and immoral practice generally go together (2Pe 2:18, 2Pe 2:19).
by reason of whom - “on account of whom,” namely, the followers of the false teachers.
the way of truth shall be evil spoken of - “blasphemed” by those without, who shall lay on Christianity itself the blame of its professors’ evil practice. Contrast 1Pe 2:12.