NO, I do not believe there is a "formal defense" per se but as you say it is an argument to make when someone tries false inflate a value of an infringement. And it is also a perfectly legitimate settlement discussion point and defense. Making an argument does not require an agreement.
In my view, it is applicable to situations where there is no copyright registration. It is a fact that many infringements do not result in money demands because of the "de minimus" argument. "It ain't worth it".
And my "list of strategies" was meant to give some specificity of what I consider controversial and cringe-inducing. I did write a disclaimer.
... keep in mind, I am not necessarily endorsing any of these strategies in themselves. Some are tools in a toolbox to be used surgically and strategically.I am not going to get into all the ins and outs of what I think and how certain controversial tactics should be used. I don't get paid enough to write freely in detail and how and what I think. I keep threatening to write a book on the subject and maybe I will one day. Meanwhile, people who really want to know what I think either has to be a good friend in business or they will have to pay for my consulting time. But I stand by my assertions. I don't limit myself to "traditional" tactics. If I did, ELI would not have been born nearly 10 years ago. ELI is living proof that unconventional tactics work in fighting back. Oscar Michelen supports ELI and continues to be a legal advisor because he saw early on how effective unconventional tactics worked.
And this whole notion that because someone has assets needs to bend over and take it up the rear is something I don't accept. It is a factor for consideration, not a determining factor. People who have assets can definitely fight back too. If you don't believe it, you are not looking hard enough. You and I will have to agree to disagree. The limiting factor is generally the person in the driver's seat.
Sometimes it isn't about the money. Sometimes it is about the principle, punchback, and not letting someone fleece you. For some people, fighting back, it is all about the money. For me, sometimes it is about the principle.
I am a bit confused. Are you saying there is a de minimum defense to copyright infringement? I have heard of the extent of the infringement being used to calculate damages, but never as a defense to liability.
Some of your listed strategies would make me cringe too if the risks associated with them are not properly explained to someone considering them. I am not sure what they all mean, but they are all 100 percent fine for someone who has nothing to lose, but to someone who has assets, a few of those tactics come with serious risk of making things worse by either inviting litigation and or increasing the chance a judge would award attorneys fees to the copyright holder and increase the award of damages.
Sure, consider being creative or unconventional. Options are good. Just make sure you know that it if you have assets, it is possible to make things worse... heck, even much worse.