You do if you're a Keynesian, because that's the whole point. Aggregate demand did increase; the economy did have positive growth. That's never been the debate really. The debate is whether the government's choice of how to spend the money it borrows to increase demand is better than the choices of millions of individual Americans.
As a side issue, I'm not sure how much I agree with your point about the government's involvement in things "only it can do well." The Internet really was not what it is now when it was a DARPA or even a predominantly DARPA-University project. It took commercial [private] participation to really create what most people now think of as The Internet. I think the same thing is also true of NASA: once the space industry had matured, it was probably a mistake for NASA to remain involved -- although I agree with you that NASA's initial participation was necessary and good. Public transportation, postal or parcel delivery, etc are all mature industries, and it's time now for the government to get out of them, or to take the same role that the military does vis-a-vis defense contractors.
But I’m not a keynesian. :) I want growth that doesn’t bankrupt this country’s future.
I agree that the best role of govt is to start something and then let private sector take on the maintenance. The internet used to consist of gray pages and gopher searches until people realized they could make big money off it.
However, US internet speeds are quite slow compared to Asian countries such as South korea and Japan because they have made investment a bigger priority.