The letter of the vows in Path is clear, but the flavor text of Oathsworn Protector hints at a strong leaning towards goodness.
Is my assumption correct that an evil, but honorable character would be able to take the path insofar as they would follow the code? Naturally, such a character would have a much more difficult time finding a willing trainer, but very few of the vows are unbelievable for an evil character to adhere to.
Generally, this Path leans toward general values of forthrightness and a code of conduct. But yes, an immoral person could theoretically take these oaths. Few do because the oaths can limit what they want to do and the penalty for not following them is immense. But depending on the culture (ex: Kali-Ishtar, Kenrei, etc) — its true — you could have murderers and “evil” people playing an oathsworn protector while staying true to their oaths.
"The End to War, the End to Pain,
these will come in Seventh's reign"