Is there any validity to this argument?
No. The nonsense of that argument is three-fold because it (1) encourages conduct that is vexatious and frivolous; (2) hinders the duty that trademark licensors have pursuant to the Lanham Act; and (3) essentially accelerates the statute of limitations for any and all claims a trademark owner may have pursuant to actual and/or unrelated offenses.
The first point is trivial. A claimant's harassment of others under pretext of producing fictitious evidence does not add merit to a claim of "eventual" offenses which might never materialize.
Mini Maid v. Maid Brigade, 967 F.2d 1516, 1518-20 (1992) is relevant to the second point: "[T]he law imposes a duty upon a licensor (such as a franchisor) to supervise a licensee's use of the licensor's own trademark". That duty is premised on the Lanham Act, and its purpose is "to protect the public from being misled about the quality or consistency of the products offered under the licensor's trademark", Id. The argument you quote would leave the public vulnerable to any subsequent, ongoing violations of trademark even if the trademark owner becomes --or has always been-- willing to comply with his duty pursuant to the Lanham Act.
Furthermore, the forfeiture implied in the quoted argument is equivalent to the absurdity of preventing a victim from accusing an offender simply because the victim cannot prove that he denounced previous offenses (which might not even have taken place).
The third weakness of the quoted argument is a consequence of the aforementioned duty. Indeed, a lack of evidence of prior policing of a trademark would impliedly preclude suits for any actual violations of that trademark, regardless of the owner's diligence in seeking a legal remedy. There are very few, if any, fields of law where such outcome would be permissible.