Horav Nissan Alpert, zl, lends insight towards understanding the anomaly of Avraham's family, i.e. Lavan, etc. Living among idol worshippers while not believing in their idols, is difficult. Yet, one cannot live in a community that worships a stone as god and not acquiesce to their practice - at least publicly. This is what they did. Lavan and his family lived a life of sham, publicly serving idols, while secretly realizing their folly.
Business is business, however.
In short, these people lived a lie. When someone lies long enough, it becomes part of his nature. He becomes accustomed to lying. He sees nothing wrong with it. He enjoys it.