I've been in plenty of fast food places with all Black employees oozing with 'tude, if I was running the place I'd have fired their asses too, so I can see where a remark like 'Get the ghetto out' might come from...also some with mostly Black employees who were polite and eager, too, oozing with positive attitude.
The original email is suspiciously short on details, the ownership's race is just the tip of the iceberg. That whole "I don't know why I was let go" really reeks of absolute bullshit.