Je déteste le français. To say "I hate French" (as in the French language) in French, you would say, "Je déteste le français." If you want to say "I hate the French" (as in the French people), you would say instead, "Je déteste les français."
It was difficult to comprehend the lesson because our teacher used many long and unfamiliar words. Primitive tribes have no way to comprehend modern inventions, and may consider them magical. When you read a sentence, it is important that you comprehend it.