disingenuously

Short definition from Wiktionary

Adverb

1. 1
   In a manner that is not frank or open; deceptively.
2. 2
   In an unnoble manner; in a manner unbecoming of true honor or dignity; unworthily.
3. 3
   In a manner that adopts a pose of naïveté, possibly to make a point or to deceive.