I think those saying it wouldn't be fair to parents who gave up work to care for disabled children are perhaps getting the wrong end of the stick. I don't think many people begrudge supporting disabled children, or those parents who cannot work as they are carers or due to their own illness/disability. I don't think that was what this proposal was suggesting.
I don't think many people would suggest that those who cannot work due to disability/illness or because they are carers for a disabled child are scroungers. I haven't seen a post on this thread suggesting otherwise.
I wouldn't support a cut in benefits to disabled children- whether their parents had 3 or more children or not. Surely their benefit relating to disability would be separate from CB/CTC (although I know there is a disability element) and thus not affected by caps to CB/CTC? I would support a cap on the number of children the state will support, as long as it was not applied retrospectively.
Benefits should be a safety net- for those who find themselves out of work or for those who cannot work due to illness or disability (or who are carers for an ill or disabled child/relative).
I don't doubt that living on benefits is not all a bed of roses and I doubt many people have children because they think they'll get rich on benefits. I do think the system allows people to have children they cannot afford to support, in the knowledge that the state will put a roof over their heads, and money in their pockets.
If you can't afford to house, clothe and feed the children you already have, then you shouldn't be having any more. If you can only afford to have more children if the state increases your benefits, you can't afford to have more children. I accept that those who lose their jobs after having children will be affected too (but perhaps that could be built into the system).
To be clear, I don't care how many children people have- as long as they can support them at the time they are conceived. Many people who are working and not receiving any benefits have to limit the number of children they have due to finances. My wages wouldn't go up if I had another child- I would be expected to fund that child on my current income. Why should it be different for those whose income comes solely or partially from the state- i.e. the tax-payer.