From the earliest days of the US' manned space program, astronauts have required several attributes:
1) the training to fly jet aircraft, and thousands of hours doing it
2) highly educated (PhDs preferred, preferably in multiple disciplines)
3) perfect (or near-perfect) physical fitness, condition, and health
4) dedication and self-sacrifice, especially the ability to push themselves as hard as needed to accomplish tasks
5) the willingness to spout the NASA party line of BS regardless of their personal feelings.
That last has not always been 100% perfect, of course, but it usually only occurred when NASA was treating the astronauts badly enough to warrant a "failure" in that requirement--it was always volitional.
So when NASA makes the decision not to repair Endeavor before it comes home, of course the astronauts are going to say, "Yes, yes, we couldn't agree more." If NASA decided that a repair was necessary, the answer would be the same. If NASA had decided to let Endeavor fall into the Pacific and have the astronauts come home in Soyuz capsules, the answer would be the same: "We agree 100% with NASA and are glad to hear that they're looking out for us."
NASA is a government agency. Everything they do is steeped in politics and the astronauts are the most visible spokespeople they have, so they must say the right things and act the right ways. (Particularly after the nonsense that cropped up around that one astronaut stalker or WTF-ever that was. I didn't even read the articles, to be honest.)
In a larger sense, this kind of thing is true of any large organization--the higher-ups almost never bad-mouth it in public unless it is doing something horribly, egregiously wrong. The astronauts are important to NASA, but NASA is even more important to the astronauts: NASA is The Only Game In Town, and if you get blacklisted (however unofficially) you'll never fly. How would you like to spend 15 years of your adult life working your ass off to accumulate the requirements and actually get in, only to end up being a supernumerary who sits at a Mission Control console and never gets to fly, because you said the wrong thing at the wrong time?
The news article I linked to is non-news. Of course the astronauts support NASA's decision. It would only be news if the astronauts were saying, "What? They're crazy! That's a freakin' crater in our heat shield! We're all going to die unless we fix it!"
That would be news. But the astronaut who said that would never fly a mission again.