There are some incompetent phone agents and they can certainly be frustrating to deal with, whether they be on AA or any other airline or any other service-oriented company.

I have seen AA or other airline agents making derogatory or negative statements on passengers' profile and/or reservation. Sometimes it is more of a "he said" vs. "she said" issue. How much this comment affects your future dealing with the company will depend on your track record and your loyalty with the company. If you regularly fly 100k+ miles on AA and spend $20K+ a year, AA is less likely to look at that one incident and count that against you vs. someone who never flies on AA with a paid ticket and only uses miles from credit card sign-ups to book award tickets.

I have had a few poor phone interactions with phone agents in the past and other phone agents who reviewed that interaction were able to review the file comments, but have always given me the benefit of the doubt as I knew what I was talking about, in terms of "airline lingo" and I have been loyal to AA as a frequent flyer for many years. But then none of my poor phone interactions are about insulting the agent or yelling at them, but rather the agent not willing or able to make changes to a reservation that I requested and refusing to transfer me to a supervisor.