Honestly, I think you are owed an explanation from AJ.
As far as written notification.
This is not NASCAR, or the NFL or the NBA or The World Soccer Federation (Whatever that is called). This is a sport that is barely hanging on. The Promoters barely make any money. I know from experience the cost envolved in putting on races. And when racers say they are coming and do not show up, many times the Promoter spends way more money than he brought in from entry fees. If the promoters was able to secure outside money from Cities to come, then they may be covered, but this is not always the case. So, honestly, I would not expect anything in writing. There is no "Law" that says anybody has the "Right" to race or participate in any sport.
It is a sucky situation. But I will say this. I have raced at Nationals where AJ was involved in one form or another. I have raced at APBA Tour Stops where AJ was envolved also and can say he has always been very fair and respectful. I got mis judged and missed the Main at nationals. Bill Haig was spotting for me (It was an LCQ). he knew where I was, so did I. But they had me 2 spots farther back. I talked to him, he took the time to walk over to scoring and pull the lap charts. He was not able to change anything but was very willing and helpful. With that, I do not believe for one second that his actions are in any form being Racist or anything else along those lines. I will go as far as to say that I believe that what every was said was enough to piss him off enough that he enacted his right as Promoter to say "You and your team are not welcome at my events any longer for this season".