That seems like a claim with no basis. Do you have anything to back it up?
Let me guess, mass trespass / right-to-roam ... what else ya got?
Your example of a news expose doesn't cut it IMO as copyright is a pointless claim in such a case (and would be covered under "fair use" clauses). You can't put the genie of a revealed secret back in the bottle but that is different to the detailed instruction on how to create a genie.
Specificially on copyright?
Lion Laboratories v Evans
Full defence accepted.
Ashdown v Telegraph (which re-established that a defence of publishing something in a way which contravened copyright was perfectly acceptable if that was the final acceptable defence and there were no other ways to present the material)
edit: ah found the quote from Griffiths https://en.wikipedia.org/wiki/Hugh_Griffiths,_Baron_Griffiths on it. "The defence of public interest is now well established in actions for breach of confidence. It also extends to breach of copyright."
So, yeah, basis.
And, no, I specifically excluded fair use by saying the full letter would be published. Or if I didn't, apologies and assume that it is implied with full knowledge that you could skirt the issue with judicious use of other alternatives.