Is one deemed an unbeliever for laughing at or not objecting to mockery of the style of some preachers which includes the saying, "A woman's chest is part of her 'awrah (intimate parts)"?

Your two friends did not commit disbelief by what you mentioned, even if they sinned by watching those reprehensible films and listening to backbiting against righteous people without condemning it. You must turn away from obsessive doubts and occupy yourself with learning the Book of Allah and the Sunnah of His Prophet, and drawing closer to Allah through worship.