Latter Days

Elder Aaron Davis, a young Mormon from Pocatello, Idaho, is sent to Los Angeles with three other missionaries to spread the Mormon faith. They move into an apartment next to openly gay party boy Christian Markelli and his roommate Julie, an aspiring singer. Christian and Julie work as waiters at Lila's, a trendy restaurant owned by retired actress Lila Montagne.
Christian makes a bet with his co-workers that he can seduce one of the Mormons, and soon realizes that Aaron, the most inexperienced missionary, is a closeted homosexual. Aaron and Christian become acquainted after several encounters in the apartment complex. When Christian accidentally cuts himself on a metal hose reel and faints, Aaron helps him indoors and cleans his wound. Christian attempts to seduce Aaron, but the hesitant Mormon becomes upset by Christian's remark that sex "doesn't have to mean anything." Aaron accuses him of being shallow and walks out. Worried that Aaron is correct, Christian joins Project Angel Food, delivering meals to people with AIDS.
Aaron's fellow missionary, Paul Ryder, has a cycling accident. Returning to his apartment, a distraught Aaron encounters Christian, who tries to comfort him with a hug. Both men are overwhelmed by their feelings and end up kissing, failing to notice the return of Aaron's roommates. Aaron is sent home in disgrace, leading Christian to confront Ryder, who is angry that Christian corrupted Aaron for no reason. Christian admits that he initially just wanted to win a bet, but says "it's not about that" anymore. Recognizing Christian's distress, Ryder tells him that Aaron's flight has a five-hour layover in Salt Lake City.
Christian finds Aaron standing in the snow outside the airport terminal. Christian confesses his love, and despite his misgivings, Aaron admits his own feelings of love. With all flights canceled due to a snowstorm, Christian and Aaron spend an intimate night in a motel. When Christian awakes, he finds Aaron gone. Aaron's pocket watch, a family heirloom, has been left behind. Christian returns to Los Angeles. In Idaho, Aaron is excommunicated by the church elders, led by his own father, Farron, who is the stake president. Aaron is rejected by his father and scolded by his mother, who tells him that he needs to pray for forgiveness. When Aaron suggests that he might be gay, his mother slaps him. Overwhelmed by despair, Aaron attempts suicide. He is subsequently sent by his parents to a treatment facility to be cured of his homosexuality.
Christian is desperate to find Aaron and locates his home address and phone number. Aaron's mother informs him that "Thanks to you, my son took a razor to his wrists; thanks to you I have lost my son." Believing that Aaron is dead, Christian spends the next few days thinking continually about Aaron. Julie discovers an entry about Christian's feelings in his cellphone journal and uses it as the basis for her new song. Christian travels to the Davis home in Idaho, where he tearfully returns Aaron's watch to his mother. During an encounter with Julie, she hesitantly shows him her new video, which upsets Christian, realizing that part of the lyrics came from his personal journal without his consent. Julie tells Christian that she hoped something good would come from it.
In the treatment facility, Aaron hears a female voice singing and investigates. He discovers a music video playing on television, the song performed by Julie. The video prompts Aaron to return to Los Angeles in search of Christian. Upon arriving at Christian's apartment, Aaron is heartbroken when a stranger answers the door. Thinking that Christian has returned to his party boy ways and moved on, and having nowhere else to go, Aaron makes his way to Lila's restaurant, having befriended the owner while on missionary work after her life partner died. Christian, who happens to be working there, comes out and is overjoyed to see Aaron alive. They reconcile and later celebrate Thanksgiving with Christian's co-workers. Lila tells everyone that, no matter what, they will always have "a place at my table, and a place in my heart".

Question: Why does Christian join Project Angel Food?
Answer: Aaron called him shallow.