I have the same problem with a dear friend, who left the Catholic church at 15 years old after a coach gave him the bible to read for himself while encouraging him Catholic traditions were wrong. He was also an altar boy, but at the time he was going to Mass the entire mass was in Latin, which was the first thing he attacked. He was not aware, until I gently educated him that since Vatican II masses are held in the native language based on the parish location.
Each time he brings something up or I mention I cannot attend one of his services or secular functions due to my commitments to my parish (for example, he did not understand Adoration before the Blessed Sacrament), I use it as an opportunity to educate him about the faith. Sure, he quickly points out that it’s not in the bible and should not be practiced, however each time I have been able to show him book, chapter and versus where it is, and remind him that if he truly believes what is written in the bible why is he refuting it? I also gently remind him that but for the Catholics he would not be reading the bible.
Stay strong, and look at it as an opportunity to show them how beautiful it is to be a Catholic! May I suggest Patrick Madrid’s book, Answer Me This, to help guide you. He addresses the major topics most Prostestants use to sway us. [BIBLEDRB][/BIBLEDRB]