Barnabas pretty much bares his soul to Maggie today, when he talks to her in the living room. He tells her she must never be frightened of him again, the way she was before, when she took her own life. It's foolish of him to talk to her that way. Maggie is barely accustomed to being Josette right now; she shouldn't be burdened yet with dealing with the past actions of Josette. But apparently he couldn't wait any longer. He just had to talk to whatever Josette was available.
It may have been that honesty from Barnabas that made the lies he told to Sam and Joe so disturbing to me. I'm not sure. I tried to find a common core between, on the one hand, the Barnabas who simply had to talk to Josette and, on the other hand, the Barnabas pretending to be so very concerned about Maggie, and I couldn't find one. I thought about what Jonathan Frid said about Barnabas’s lies, and I tried again, and still I couldn't find the common core. Barnabas had completely isolated his true self from the persona he was showing to Sam and Joe.