"Dishonest" means something that is trying to cheat, deceive, or swindle someone. "Insidious" means something bad that sneaks in gently and gradually, so that you don't even notice what is happening until it is too late. "It is as insidious as it is dishonest" is really just a way of saying "it is both insidious and dishonest." It is doubling the insult or the criticism. The fact that it is insidious is just as serious as the fact that it is dishonest. "The way in which Volkswagen cheated on the emissions test was as insidious as it was dishonest." It was dishonest because cars that should have failed the test, passed it. It was insidious because the cheating was done secretly, by computer software inside the car; the car owner, the inspection station doing the test, the dealer selling the car--none of them knew about it. It was insidious.

"You are as insidious as you are dishonest." This means the person appears to be honest and harmless, while actually spreading lies and causing problems. Insidious means bad, but without being obvious, like a disease with no noticable symptoms. I hope this helps! Just ask if I can clarify anything!