I am particularly grateful for the "How's the baby doing?" example, because it so clearly illustrates the ethical problem and the aspect of coercion.
For most of the "difficult" people we have to deal with on a regular basis, we soon learn that it's possible to steer them to a topic they find more interesting than being obnoxious (or being whiny, or whatever form their "difficultness" takes). It's like the standard principle for training a puppy: Don't punish the pup that's chewing on a shoe, hand the pup something that it's okay to chew on. 
The question is: Is it ethical to use that tactic with another human being as long as you're doing it for Good Reasons -- for example, when your goal is to avoid having your workplace flooded with toxic language for the next twenty minutes or so, with all the negative consequences that kind of contamination has for people's health and well-being and morale?
For me, the most important thing is being aware that this is an ethical question, and that when someone decides to take control of the language environment in this way they are fully aware that that's what they're doing and understand that they're responsible for the consequences of their decision.
. In my own childhood, I saw this done fairly often exactly as you'd do it with a puppy: A standard tactic for deflecting a man who was obviously heading toward a display of Very Difficult language behavior was to hand him a banjo or a guitar. Worked like a charm.