I have also seen it used defensively by people. I'm trying to think how to word this so it doesn't sound judgy because that isnt how its meant.
As parents we all know we are never able to be perfect, so we make decisions along the way as to what things we are going to prioritise as family standards and what things we are going to be more relaxed about. For example whether to only feed organic food to weaning baby, whether to allow baby to watch TV, whether to not allow child/baby to have chocolate etc etc. But sometimes you find that when other people find out your priorities, if they don't match theirs, they accuse you of being PFB.
A good example is that I personally do not let my DD (6months) wach TV & I don't turn TV on if she is awake. I'm not bonkers about this, at my parents' house the TV is sometimes on and I don't make a fuss but my preference is that she doesn't watch TV. My choice.
My friend lets her baby (same age) watch TV quite regularly, it helps her pass the time of day to have the TV on and her DD sometimes watches football with daddy. "So what" I say. Her choice. But my friend got very defensive with me and said I was 'precious' when it came up in conversation that I don't choose for my DD to watch TV.
On the other hand, this same friend is a great cook. She makes everything from scratch with natural organic products (bread/yoghurt/homous etc) for her DD. I don't do this, partly because I can't and partly because for me it isn't a priority. But I don't think she is being PFB, she is just making a decision as to where her priorities lie for her DD.
I think as more children arrive to juggle, people have to change their priorities. I'm sure when I have another baby, I will find it much more difficult not to use the TV as a babysitter for DD when I'm dealing with a second child. But that doesn't mean I'm being PFB at the moment because I have the luxury of only one child to consider.
I think this is what I find irritating about this comment. Sometimes if does feel like a defensive reaction, as if people percieve by making a particular choice regarding how you raise your child, is a personal attack on others who have made different choices. When really, it is nothing to do with them at all.