"Mistaken as" vs. "mistaken for"
Usually, "mistaken for" is used when the speaker is refering to something with an identity (anything with mass)- that is a person, or an object.
Ex: He was mistaken for her husband as he was sitting by her side.
"Mistaken as" is used when the speaker is refering to some kind of an action, say, judgement in this question.
Ex: Since he spoke like an angel, his intentions were mistaken as good [or honorable]