I think the words "black fungus", "spare tire" and so on are too hurtful, but it is undeniable that it is indeed very graphic. He said you are "black fungus" when you have to combine the context in which he said this sentence, he may be just because the word is fun to say casually is not necessarily. You shouldn't get carried away just because of one word. Trust me, if he doesn't love you, you'll definitely feel it elsewhere.