It's always okay to politey and professionaly not waste people's time. Don't come across as judgemental, angry, or anything similar or you risk burning bridges you may not even realize you have.
From the brief description, it sounds like the guy was showing a bit too much emotion in leaving. Also - just because an interview process seems harsh doesn't mean the company is harsh - the interview is one thing, the job is often quite another - results tend to speak for themselves regardless of culture (and as long as you aren't a snob or jerk to your co-workers)
If a seasoned, experienced professional doesn't get that, maybe they aren't a good fit...
From the brief description, it sounds like the guy was showing a bit too much emotion in leaving. Also - just because an interview process seems harsh doesn't mean the company is harsh - the interview is one thing, the job is often quite another - results tend to speak for themselves regardless of culture (and as long as you aren't a snob or jerk to your co-workers) If a seasoned, experienced professional doesn't get that, maybe they aren't a good fit...