Now I don't doubt that courses in logic, epistemology, and ethics can help inculcate habits of critical thinking and good judgment. And it may also be true that philosophy has a unique role to play here. So, while it is true that every discipline teaches habits of critical thinking and good judgment in that discipline, there are plenty of issues that are not discipline-specific, and these need to be addressed critically as well.
What I object to, however, is the notion that philosophy needs to justify itself in terms of an end external to it, and that its main justification is in terms of an end outside of it. The main reason to study philosophy is not to become a more critical reasoner or a better evaluator of evidence, but to grapple with the ultimate questions of human existence and to arrive at as much insight into them as is possible. What drives philosophy is the desire to know the ultimate truth about the ultimate matters. Let's not confuse a useful byproduct of philosophical study (development of critical thinking skills) with the goal of philosophical study. The reason to study English literature is not to improve one's vocabulary or to prepare for a career as a journalist. Similarly, the reason to study philosophy is not to improve one's ability to think clearly about extraphilosophical matters or to acquire skills that may prove handy in law school.
Philosophy is an end in itself. This is why it is foolish to try to convince philistines that it is good for something. It is not primarily good for something. It is a good in itself. Otherwise you are acquiescing in the philistinism you ought to be combating. Is listening to the sublime adagio movement of Beethoven's Ninth Symphony good for something? And what would that be, to impress people with how cultured you are?
To the philistine's "Philosophy bakes no bread" you should not respond "Yes it does," for such responses are patently lame. You should say, "Man does not live by bread alone," or "Not everything is pursued as a means to something else," or "A university is not a trade school." You should not acquiesce in the philistine's values and assumptions, but go on the attack and question his values and assumptions. Put him on the spot. Play the Socratic gadfly. If a philistine wants to know how much you got paid for writing an article for a professional journal, say, "Do you really think that only what one is paid to do is worth doing?"
Admittedly, this is a lofty conception of philosophy and I would hate to have to defend it before the uncomprehending philistines one would expect to find on the typical Board of Regents. But philosophy is what it is, lofty by nature, and if we are to defend it we must do so in a way that does not betray it.
It might be better, though, not to stoop to defend it at all, at least not before the uncomprehending. It might be better to show contempt and supercilious disdain. Not everyone can be reasoned with, and part of being reasonable is understanding this fact.