Based on your description it seems pretty clear that your travelers met the requirements outlined by AS on the web.

Most AS employees are friendly and helpful, but as with virtually any company there are some bad apples.

I would write a concise (facts only, non-emotional) message to customer service and explain what happened, Be sure to provide the travel dates, flight numbers, and reservation numbers. Express your concern that you paid for the seats and obviously expect a refund in cash, but also that the gate agent was rude and unfamiliar with the documented policies and should receive additional training on the exit row policies and appropriate customer interaction If you feel additional compensation is due, spell out what you are looking for. If the response from AS is not satisfying, file a DOT complaint.