So two people commit suicide to prove a point. What happens when Bitsy exposes the fact that it was a setup?
She can't, due to her obligation as a journalist to David to keep it off the record. So, she'll have to take it to the grave.
That's what the film makers are trying to promote. In truth, a journalist's ethics would oblige her to reveal the actual story, thus destroying Gale's argument against capital punishment (i.e. Gale had to commit fraud to break the system, so his argument that the system is inherently wrong loses all credibility. You can't claim something doesn't work if you intentionally break it). Journalists aren't lawyers or priests - their ethics are to the truth of the story, not to promulgate a fraud in the name of keeping a confidence. Journalism 101.
That is, of course, assuming that all journalists keep to this code of ethics, which is debatable at best. Just as many journalists work hard to conceal the truth, especially on an issue as politically and socially charged as this, as try to reveal it, whether by diversion or some other method. There is every chance that Bitsy will keep it "off the record"; it just depends on how she feels about it.
Moreover, there's every reason to have Dusty charged for some equivalent to "perverting the course of justice", and journalistic ethics wouldn't prevent going to the police with that (even if they might prevent using it as part of a story).
Remember that Gale and associates have committed multiple crimes. From as trivial as filing a false police report to perjury, fraud, criminal libel, and conspiracy to commit murder (as assisted suicide was and remains an illegal act in Texas), everyone involved in the scheme is a multiple felon. No journalist, regardless of their political feelings, is going to pass up reporting on that kind of story.
How twisted is it that Gale knowingly gets Bitsy and Zack to watch a woman commit suicide in a horrible manner, all just to promote a political point? Even worse, Dusty letting them see the real suicide tape, knowing they won't make it in time to stop the execution.
What will Gale's son grow up thinking of his father, now? Either as a murderer or horrible liar?
Gale and his co-conspirators intentionally involve an unwilling Bitsy and Zack in a conspiracy to commit judicial fraud, then ask them to cover it up.
How will the exposure of Constance's staged fake rape negatively impact other cases of reported rape?
No one except his wife knows. It hasn't been exposed to anyone besides her.
As a rather dark example of Fridge Brilliance, the plot of the movie makes more sense if you look at it as a pair of lonely, deeply depressed friends-one dying of an incurable illness, one ruined by false accusations and a divorce-agreeing to kill themselves in a suicide pact, and using a protest against capital punishment as an excuse for their decision. Especially when you consider that if and when Constance dies of leukemia, David will lose his only real friend and have even less to live for.
A fair interpretation of the events.
On the more meta level, this film did a massive disservice to the anti-death-penalty position, as it presented adherents as being so deranged as to require a completely contrived fantasy situation to justify their stance against it, despite favoring that view. That's precisely why Roger Ebert savaged it.
Gale's entire scheme depends on finding just the right reporter and a whole set of far-from-certain events to occur in order for his story to come out. It's more than a Batman Gambit or even a Thanatos Gambit, but really a Contrived Coincidence.
More to the point, who's to say that his lawyer wouldn't voir dire the "right" jury and land him a sentence of life without parole?
His lawyer was in on the scheme, and intentionally represented him poorly as part of it.
All it takes is one person to avoid the death penalty, which is required to be unanimous, just like the verdict. That's not a good bet to make that there won't be one person on a jury that will think Gale did it but doesn't deserve to die for it.
Jurors have to be "death qualified", meaning confirm that they are willing to vote for death if the defendant is convicted. Studies have shown that those so qualified are also more likely to convict overall. So this was a fair bet, especially aided by poor counsel and quite a brutal (apparent) rape-murder.