If Alice doesn’t mean for her second sentence to be totally redundant—or if she is able to interpret Bob’s response as an intelligible (if incorrect) statement of disagreement with her second sentence—then that suggests her second sentence actually constitutes a substantively normative claim.
I don’t think you can declare a sentence redundant without also considering the pragmatic aspects of meaning. In this example, Alice’s second sentence is a stronger claim than the first, because it again contains an implicit clause: “If you want to get protein, and you don’t have any other relevant goals, you should eat meat”. Or maybe it’s more like “If you want to get protein, and your other goals are standard ones, you should eat meat.”
Compare: Alice says “Jumping off cliffs without a parachute is a quick way to feel very excited. If you want to feel excited, you should jump off cliffs without a parachute.” Bob says “No you shouldn’t, because you’ll die.” Alice’s first sentence is true, and her second sentence is false, so they can’t be equivalent—but both of them can be interpreted as goal-conditional empirical sentences. It’s just the case that when you make broad statements, pragmatically you are assuming a “normal” set of goals.
If she is able to interpret Bob’s response as an intelligible (if incorrect) statement of disagreement with her second sentence
It’s not entirely unintelligible, because Alice is relying on an implicit premise of “standard goals” I mentioned above, and the reason people like Bob are so outspoken on this issue is because they’re trying to change that norm of what we consider “standard goals”. I do think that if Alice really understood normativity, she would tell Bob that she was trying to make a different type of claim to his one, because his was normative and hers wasn’t—while conceding that he had reason to find the pragmatics of her sentence objectionable.
Also, though, you’ve picked a case where the disputed statement is often used both in empirical ways and in normative ways. This is the least clear sort of example (especially since, pragmatically, when you repeat almost the same thing twice, it makes people think you’re implying something different). The vast majority of examples of people using “if you want..., then you should...” seem clearly empirical to me—including many that are in morally relevant domains, where the pragmatics make their empirical nature clear:
A: “If you want to murder someone without getting caught, you should plan carefully.”
B: “No you shouldn’t, because you shouldn’t murder people.”
A: “Well obviously you shouldn’t murder people, but I’m just saying that if you wanted to, planning would make things much easier.”
I don’t think you can declare a sentence redundant without also considering the pragmatic aspects of meaning. In this example, Alice’s second sentence is a stronger claim than the first, because it again contains an implicit clause: “If you want to get protein, and you don’t have any other relevant goals, you should eat meat”. Or maybe it’s more like “If you want to get protein, and your other goals are standard ones, you should eat meat.”
Compare: Alice says “Jumping off cliffs without a parachute is a quick way to feel very excited. If you want to feel excited, you should jump off cliffs without a parachute.” Bob says “No you shouldn’t, because you’ll die.” Alice’s first sentence is true, and her second sentence is false, so they can’t be equivalent—but both of them can be interpreted as goal-conditional empirical sentences. It’s just the case that when you make broad statements, pragmatically you are assuming a “normal” set of goals.
It’s not entirely unintelligible, because Alice is relying on an implicit premise of “standard goals” I mentioned above, and the reason people like Bob are so outspoken on this issue is because they’re trying to change that norm of what we consider “standard goals”. I do think that if Alice really understood normativity, she would tell Bob that she was trying to make a different type of claim to his one, because his was normative and hers wasn’t—while conceding that he had reason to find the pragmatics of her sentence objectionable.
Also, though, you’ve picked a case where the disputed statement is often used both in empirical ways and in normative ways. This is the least clear sort of example (especially since, pragmatically, when you repeat almost the same thing twice, it makes people think you’re implying something different). The vast majority of examples of people using “if you want..., then you should...” seem clearly empirical to me—including many that are in morally relevant domains, where the pragmatics make their empirical nature clear:
A: “If you want to murder someone without getting caught, you should plan carefully.”
B: “No you shouldn’t, because you shouldn’t murder people.”
A: “Well obviously you shouldn’t murder people, but I’m just saying that if you wanted to, planning would make things much easier.”