This popped up during a conversation. My friend said (roughly):
Some vegetarians don't eat meat. Why not fish?
To me, this felt somewhat weird. Her intent was to ask, if some vegetarians refuse to eat meat, why are they okay eating fish? The part that felt weird was the "why not".
Suppose she had said instead:
Some vegetarians refuse to eat meat. Why not fish?
Then this would be equivalent to:
Some vegetarians refuse to eat meat. Why don't they refuse to eat fish?
But by saying:
Some vegetarians don't eat meat. Why not fish?
She's really saying:
Some vegetarians don't eat meat. Why don't they don't eat fish?
Which is a double negative. Am I right? Or am I completely crazy here?