Absolutely not. Bush's number one problem is not being able to say "no". I was commenting on them including homeland security as an unnecessary expense.
You need to critique what they actually said, not what you make up out of whole cloth.
DISCRETIONARY spending includes everything that is not specifically required by law. It has nothing to do with how "necessary" the expenses in question are, only with how much control can be immediately exercised over them.
The proper response to an increase in necessary spending is to make corresponding cuts in non-necessary spending. The ongoing and blatant failure to do so is, quite rightly, criticized by Cato.