I think two things need to be pointed out here:
First, we have no actual proof he really sent the letter. He could have just written it out of frustration and then posted it on APC just for fun without ever actually sending it to SWA.
Second, I think this letter points to the frustration many of us have had with this industry. Particularly with seemingly arbitrary rejection letters even before having the chance to interview. We all deal with those frustrations differently. I have had my fair share of raw deals in this career. It happens and eventually you just get to a point where you just make the best of what you have.
The most frustrating thing I have experienced was never getting a chance to interview at a certain legacy airline that was hiring everyone else from my company. I had more than the competitive requirements, no accidents, incidents, violations, or failures. I was a check airman and had seven internal letters of recommendation. I was promised over the course of four job fairs of being on the short list for an interview call and one of my internal recommendations was a good friend of a base chief pilot. He had the base chief pilot call to the HR department to check on my application and confirmed I would get a call in less than two weeks. Seven years later I am still waiting for that call (not really, I have moved on). After racking my brain trying to figure out why I never got a call it was finally, unofficially, revealed to me why. I have the misfortune of having the same, fairly rare, last name as a well despised, notorious, former management pilot of this airline. Nobody at this airline wanted to take a chance of hiring a person who was related to that guy, so I was immediately blacklisted as soon as my application hit the pile. I never stood a chance. I could have commanded five space shuttle missions and been a former Thunderbird, they still never would have given me a chance.
So whether this guys letter was real or not, I certainly understand the frustration vented in his letter and I am sure many of us do as well.