I have yet to hear anyone say that LE is the bad guy. But LE has a job to do, and that is to find who has committed a crime. One of the techniques that they use is to interrogate people that they are suspicious of, and those interrogations are not pleasant.
This family sat through long sessions of interrogation and did not "crack" and then said "no more". Why didn't they crack? Either because they are darned good liars (which, if you understand the Reid Technique of interrogation, is rather unlikely), or they are innocent. In either case, they have a valid reason to not want to go sit in the interrogation room again.
In the meantime they have been answering questions - but LE has not only allowed the public to believe otherwise, but they have actually encouraged it - until they are asked point blank, and they have no choice but to admit that the parents are, in fact, cooperating.
That doesn't make LE bad, it just is two different sides of the same situation. Some people can see and understand both sides without saying one is right and the other is wrong, and some people can't. I am one of the ones who can see both sides.