From the management:
I am in receipt of your letter regarding complaints from the person in the apartment below you.
After reading the letter I have come to two conclusions.
1. You have been overly compliant with respecting the issues of the neighbor.
2. You have rights as a resident and do not need to be hassled by a neighbor.
I have written him a letter and if this continues please inform the office immediately. If he knocks on your door you can choose not to answer it and call the resident manager @ XXX-XXXX. You can call them at any time and they will respond and come over to address the problem.