Don't be daft. Things don't have to be interchangeable to draw comparisons. Dogs and cats are not interchangeable but if someone said "I don't like dogs because

Don't be daft. Things don't have to be interchangeable to draw comparisons. Dogs and cats are not interchangeable but if someone said "I don't like dogs because they shed. I am a cat person." we should be able to point out that cats also shed without fear of someone saying we think cats and dogs are interchangeable. Edit: And no... I don't think animal hair and the Holocaust are interchangeable.