First, I'm sorry to hear of your poor experience.
I felt that this was also the case when I flew from JFK on QR the other day, where they would weigh your carryon and were rather strict with the weight of the check-in baggage (even in J). However, whilst the agent(s) may have not been the most helpful, they did operate by the rules that are written on the ticket, which does mention the weight limit of each item.