How incredibly small-minded. I respect people who've tried something and decided it's not for them. But to never even try a different kind of food? I suspect it's less that he's found what he likes and more that he's scared he'd find out he actually liked something else better, and has wasted those 10 years.
How incredibly patronizing.
Have you considered that people have different tastes? Personally, I hate eating; if I could take a pill to replace all my nutrition needs, I would in a heartbeat, even if it costs more than my current dietary expenses.