All parents do this, even the ones that both work.
And of course you can't get both the BB and PPL!
I agree with some of your points but at the end of the day, the Govt owes it better for the economy to have people working and paying tax and not claiming as many benefits. So it makes sense that their policies will reward that.
They are not going to force anyone to work who doesn't want to, they're just not going to fund that decision as much as they currently do. Which yes, means that some parents won't have the luxury of staying home that currently do.
Being a SAHP doesn't help the economy in terms of dollars as much as being in employment does. Just a fact not an insult. And dollars are more important to the Govt than car pooling and canteen duty (I'm not being sarcastic here, just referring to an earlier post). People who don't work also claim more benefits so its lose/lose for the Govt.
I don't think you can blame them for moving in this direction, even if you don't like how it affects you personally. Much like I don't like having a vastly reduced PHI rebate now, but I can understand why they have done it.