I'm with you 90% of the way, but I don't understand this argument.
It's like Hilary's emails or WikiLeaks; "But it came from hackers!" Who cares, if it reveals legitimate criminal activity. There's no equivalency.
If we wouldn't trust the evidence from a prosecutor by itself, why would we trust evidence from an entity fulfilling the same role in the court of public opinion?
Take the OJ Simpson criminal trial, for instance.
...or the Lori Loughlin college bribery and money-laundering scandal.
...or the Aaron Swartz travesty.
War crimes for one can be far more "transactional" and horrific with two sides. Side A is shooting surrendering soldiers! Now censor the false surrender killings of side B that prompted this.
Or Side C arming child soldiers and teaching them to shoot invaders until they stop moving - except it happened after Side D started waging no holds barred genocide and horrifically arming children was /the right thing to do/ lacking other alternatives. Censor Side D's atrocities as "inappropriate" content and Side C trying to survive now looks villainous instead of the desperate and unseemly but technically moral move it is.