To their credit, at least you got a reply to your letter. Well done for standing up for yourself. Unfortunately for many who stand up for themselves in this way find themselves in the employer black book and are unlikely to work in the industry again, even those with thousands of hours of experience. Like they said, they have 50 pilot resumes on file and many of those would be prepared to work for $100 per week. That is the problem with the industry, it always has been, and probably always will be.
I just hope for you that your name hasn't found it's way into the black book, and you can move on to find gainful employment in the industry.