Is the NTSB hostile to pilots, as depicted in the movie 'Sully'?
I think it is quite unfair to paint the NTSB investigators as villains just for the dramatic effect when nothing of the sort happened in real life.

It is the job of the NTSB to investigate all possible reasons for the accident. It includes pilot error among other things. They were doing precisely that in the actual investigation. Among other things, the NTSB concluded that:


The captain’s decision to ditch on the Hudson River rather than attempting to land at an airport provided the highest probability that the accident would be survivable.


The simulations carried out by the NTSB were part of the investigation and were much more elaborate:


The pilots were fully briefed on the maneuver before they attempted to perform it in the simulator. The following three flight scenarios were flown:
(1) normal landings on runway 4 at LGA, starting from an altitude of 1,000 or 1,500 feet on approach;
(2) attempted landings at LGA or TEB after the bird strike, starting both from zero groundspeed on takeoff from runway 4 at LGA and from a preprogrammed point shortly before the bird strike and loss of engine thrust; and
(3) ditching on the Hudson River starting from 1,500 feet above the river at an airspeed of 200 kts.

Note that the NTSB clearly mentions that the pilots were briefed before the simulation. NTSB noted clearly in its report that immediate turning of the aircraft after the bird ingestion did not reflect what could've been done in real world:

The immediate turn made by the pilots during the simulations did not reflect or account for real-world considerations, such as the time delay required to recognize the bird strike and decide on a course of action.

The simulations (along with the case where there was a 35 second delay to account for pilot response) was done entirely by the NTSB with no input whatsoever from the flight crew. As The Guardian notes:

And then the investigators – not Sullenberger – asked a pilot to wait 35 seconds before attempting an airport return. That flight didn’t make it. Consequently, the NTSB was unequivocal in its declaration that the Hudson was the right call.

Actually, the movie was so inaccurate in the portrayal of the NTSB that the real people involved asked the names of the investigators in the movie to be changed:

... a draft script included the names of real-life NTSB officials, but Sullenberger - who is an adviser on the film - requested they be taken out.
He said, ‘These are people who are not prosecutors. They are doing a very important job, and if, for editorial purposes, we want to make it more of a prosecutorial process, it ain’t fair to them,”’ said Hanks.

There is no evidence to determine that the NTSB acted in the interest of insurance companies (or anyone else) in this investigation. The situations in which an insurance company is liable depends on the particular policy (as far as I know, liability is usually for negligence).
While the investigation may not be perfect, there was no kangaroo court anytime during the investigation. There was no attempt at public lynching, as The Guardian notes:

In fact, in his memoir, Sullenberger reflects that he was “buoyed by the fact that investigators determined that Jeff and I made appropriate choices at every step”

There was no cover-up by the NTSB and there was no Kangaroo court (you can easily look up the public hearings in this case) to pin everything on the flight crew on behalf of somebody else. Though not perfect, there is nothing to suggest that the investigation was not conducted professionally.
It is sad that the movie portrayed officials performing their duty as villains just because it was decided that the people would rather have the ancient good Vs evil show in the movie rather than the truth (while I'd have to agree that the movie would've looked more like documentary otherwise, that is no excuse).
The problem though, is that more people will be seeing the movie than reading the report or looking up the actual investigation that people will have a entirely uncalled for negative opinion of the NTSB, which may affect the future investigations. As Robert Benson who carried out investigation on the Flight 1549 noted in an article:

&quot;I do not know why the writer and director chose to twist the role of the NTSB into such an inaccurate depiction. .... The movie may actually be detrimental to aviation safety. Pilots involved in accidents will now expect harsh, unfair treatment by investigators. They and others who see the movie will now believe that the NTSB enters into any investigation with preconceived notions, and that we are intent on destroying reputations. Simply untrue. The NTSB is the best friend an airline passenger never gets to meet.&quot;