So by your standard, the works of Nietzsche are worthless because he was a strident anti-rationalist, and his works of literature contain many (mostly purposeful) contradictions?
Philosophy is only useful for generating questions anyway, so the harm is minimized - but yes, it's not something you should base your worldview on.
Rationalism, which you seem to be an ardent supporter of, is a strain of philosophy. We all have some epistemological system we live by, so discrediting philosophy on its whole is not an option.