When I hear something like this, which is rarely, all I do is make sure that the person that said it knows that they were overheard.
Everyone's under pressure from this merger, employees too, and there are bound to be instances of saying things that you might not have said had you thought about it first.
I cut them some slack as long as they do their job well, and don't take it out on the passengers. If they start to treat us without courtesy, my approach is to push back (verbally) gently but firmly, for example repeating back to them what they said with a question mark.