People aren't perfect. It's an understandable fact. When a character recognizes this, they might try to improve or eliminate a stock vice (alcohol, masturbation, swearing, eating sweets), which in any other episode would be portrayed as completely normal. But for this episode, the problem must be completely eradicated. Beyond clean living, this is a sterilization of a minor imperfection. This is common in episodes revolving around New Year's Resolutions, dieting, abstinence, re-finding religion, etc. Expect a family character to force others to participate alongside them.