Just that really. Was at someone's house with 10 month old baby watching cbeebies, I jokingly comment that I will delay putting the tv on as long as possible (in reference to the irritating song that was currently on) - cue babies mum getting hugely defensive about how much tv the baby watches, how it's only on before bed etc etc and lecturing me about how it's a godsend when you need to distract them for 5 mins so you can go for a wee.
I in no way suggested that I thought she was doing anything wrong, so why such a defensive reaction?