McCain and Veterans
It's worth noting that not only did John McCain oppose Jim Webb's bill expanding educational benefits for veterans, but he has a long track record of fairly stingy behavior on veterans' issues. As Hilzoy puts it "McCain has supported basic appropriations for vets. However, when there are two competing proposals, he generally chooses the cheaper one, and often, when only one proposal to increase benefits is available, he opposes it."
One sort of wonders why this is. McCain's clearly not some kind of dogmatic libertarian, and he certainly seems to have a great deal of emotional attachment to the military. I believe the particular military family in which he grew up was a bit idiosyncratic in actually being composed of life-long military officers rather than veterans (Webb, by contrast, is also from a military family and is clearly very influenced by his military background but after graduating from the academy put his time in then took advantage of veterans' benefits to move on to other things) as such. Or maybe he just takes very seriously the idea that we can't make the benefits too generous lest it undermine our ability to endlessly prolong the war in Iraq.