While less likely to lead to wars and political upheaval than religion, I see the same theme and challenges play out with many other "lifestyle" beliefs. When I say lifestyle, I mean a conscious deviation from passive existence, generally based on a core concept or value. Examples include abiding by a certain nutritional philosophy, being an athlete, and pursuing a vocation instead of a job. It could even be committing to being a certain type of partner or parent. When we embrace a lifestyle choice, it becomes part of our identity...you are an athlete, even when you aren't running...you are a teacher, even when you aren't teaching. A lifestyle isn't put away at the end of the day.
If you know me, or have read many of my previous ramblings, you'll know that I didn't intend to become a runner, let alone compete in 100 mile endurance events. Though exposed to a variety of sports growing up, I was a participant, never an athlete. Even today, amidst two-a-day workouts and a vague outline of future race plans, I consider myself more of an adventurer of the athletic (and possibly extreme) variety. For me, running was the introduction to the athletic lifestyle that enriched and expanded my desire and ability to say "yes!" to any adventure. Training is done with the aim to experience more and accomplish new things in the limited time I'm given, never to impose restrictions. That's not to say it's always fun, but even on the days it's not, I'm doing the work today so I can have more fun in the future.
Unfortunately, once you embrace a lifestyle and experience the rush of positive self-changes, it's sometimes tempting to be overzealous, defensive, and even judgmental toward those who haven't made that same choice (insert born-again evangelist, recent Paleo convert, etc. here). It's all with the best intentions...clearly you just haven't found the true way to live yet and it would be irresponsible, even immoral, to not at least try to bring you along with them. As we settle into the lifestyle, giving into these tendencies can lead to alienation, a close-minded world view, or eventual disillusionment with the lifestyle itself.
When we adopt a lifestyle, whether that of a Christian, triathlete, vegan, or writer we have a choice. We can use it as a lens to find brotherhood and connection with both ourselves and the world around us, or as a tool for separation that narrows our view of the world. Whether you look for connection or division, you will always find what you seek.