There are two good reasons for bush to have vetod the Iraq Supplemental Funding bill.
First, as he noted in his veto remarks:

…the bill is loaded with billions of dollars in non-emergency spending that has nothing to do with fighting the war on terror. Congress should debate these spending measures on their own merits — and not as part of an emergency funding bill for our troops.

He is absolutely correct. No bill should include spending not directly related to the subject of the bill. The dems should be ashamed of themselves for continuing this behavior.
w should also be ashamed of himself for calling this out given his abysmal failure to use this as a valid reason to wield his veto for the past 6 years.
The second, which he forgot to mention, is that the money won’t be needed. That he is ending this misbegotten invasion and occupation immediately.
Since he forgot, congress should not.

Rather, congress should do the only just and reasonable things that they can do: withdraw their approval for the use of military force in Iraq and provide no additional funding.

w in his veto remarks:

Without a war funding bill, we add to the uncertainty felt by our military families. Our troops and their families deserve better — and their elected leaders can do better.
Here in Washington, we have our differences on the way forward in Iraq, and we will debate them openly. Yet whatever our differences, surely we can agree that our troops are worthy of this funding — and that we have a responsibility to get it to them without further delay.

Our troops do deserve better.
Our troops do deserve the best we can give them.

Yes, george, our troops deserve to be brought home now!