disingenuously

vilpillisesti, petollisesti In a manner that is not frank or open; deceptively.
1874, Govenor Musgrave, "Capital: Mr. Mill's Fundamental Propositions", The Contemporary Review 24: 745.

Instead of inquiring why the facts oppose the theory, and where the explanation is to be found for this remarkabe discrepancy, he disingenuously endeavours to give reasons for "the causes which operated, and do commonly operate, to prevent these extraordinary drafts on the productive resources of the country from being so much felt as it might seem reasonable to expect."

The letter's false intent trumps any truths within, which one would expect of a woman who disingenuously calls herself Fidessa.

Churchill, a month later, would memorably if disingenuously describe Lend-Lease as a matter of "Give us the tools and we will finish the job." Roosevelt, a few days earlier, had described it a bit more prosaically, but no less disingenuously, as the equivalent of lending a neighbor whose house was on fire a garden hose, expecting to get it back when the fire was out.