Would it be impolite to tell someone "do whatever you want" if you have been asked "what was the right thing to do"? does it mean you care less?
My original answer (in the comments above) to this question interpreted the response "do whatever you want" as being inherently evasive: "Whatever else 'Do whatever you want' may be taken to mean, it means that the speaker is unwilling to commit to expressing a view about the propriety of the conduct that the questioner is asking about."
Returning to this question a few days later, however, I think that whether the response provides useful advice or merely avoids offering a direct opinion depends on the context in which the answer is offered, as Mari-Lou A's comment above suggests.
For example, if the question is along the lines of "Should I let Person X tell me to do, or should I do whatever suits my fancy, or should I try to find a middle ground between those two options?" the response "Do whatever you want" advocates in favor of the second option—and cannot reasonably be interpreted as signifying that the answerer doesn't care what the questioner ends up doing.
On the other hand, if the question is something like "Should I just keep waiting and hoping that you might change your mind and decide to marry me, or should I give up all hope?" the response "Do whatever you want" indicates a terminally frigid level of indifference.
I suspect that most situations fall somewhere between those two poles, but I would guess that the instances where "Do whatever you want" is intended encouragingly and supportively are somewhat fewer than the instances where it is intended to shrug off further conversation on the question.