What was reportedly on the facebook page was derogatory and bad. However, it was a private FB group, not a public tweet, and they did not say it while on the job or in their official capacity. (That we know of)
As American citizens, they have the right to say whatever they like on their own time. Even when it is inappropriate, it is still their right to free speech.
Compared to some of the things AOC says in her official capacity, she is the last one to be throwing stones.