Not sure how Canada is, but that is all you need here to file discrimination.
I worked in Motorola HR for 6 years. I can tell you the shit that goes on in HR departments... well it is amazing that any business around is still operating and sued to death.
If they gave you a warning one time - written, verbal, or telepathically relayed to your dead aunt to tell you through the Ouija board - they are SUPPOSE (here, not sure of up there) to provide you with additional counseling/training to ensure you succeed. For instance you cuss out a customer on the phone, bing! mandatory phone etiquette classes. You grab a female coworkers ass - oohhhh free doughnuts in the sexual harassment awareness course.
For real, it is 10x harder to legitimately fire an employee for common violations nowdays than ever before. You got to do something really really stupid or really really violent to get fired and not have a strong case.