I completely disagree that it is a lifestyle. I’d like examples of the facts you mention in a general sense. Be specific!
I’m going by facts known by studying researchers and authors who have made it their life’s work to study general aspects of social behavior and how it relates to sexual identity. Plenty I have studied in my MA program contradicts your claim. You can believe what you want, but most all ethnographic empirical research, surveys, participant/observation, focus groups, etc., say otherwise.
I highlighted a section from your response. It makes sense that you observed changes in some folks’ sexual identity. It is fluid, not fixed. There are some folks are out there who might identify as bisexual, but assumed to be straight or gay based upon whether they’re presently dating a man or a woman. Or, some people identifying socially as straight have discovered later in life that something just wasn’t right, and they start dating someone from the same gender or get a sex change.
If you find it immoral, that’s your belief and as much as I find it damaging to fellow Americans, I’m not here to tell you what to think or how to feel. But I will criticize and challenge your position that non-straight relationships and sex represent merely a lifestyle.