I also think you're being too hard on yourself here. Sure, it will be helpful for you to learn to interact with difficult people, and to bite your tongue when frustrated. But frankly, most of us have limited success with that even by late in our careers. It appears to me that the recruiter could have been a lot more helpful, particularly at the end where you flat-out explain you have Unix and Linux experience and they still insist that your email never said so.