If you can't come up with an argument against that then you're not trying hard enough. The most obvious is that sharing a mod is free speech and ought to be protected as such.
It's also unclear how mods contribute to copyright infringement in any meaningful way. I'm having trouble finding details about exactly what Neimod's mods entailed, but most mods I have experience with require an existing copy of the game.
If freedom of speech gives individuals a license to say anything in any medium, then this means that artificial scarcity is inconsistent with free speech.
If artificial scarcity is immoral, then all information products are immoral.
(Note that as a practical matter I suspect that Nintendo only cares about "hacking" insofar as it undermines sales. I can't see why they would care about people modifying the games or equipment they own. I can totally see why they would care if someone invented an SD card cartridge for the 3DS that allows you to run every game ever written from it. Such a device, if mass produced and sold for profit, is clearly intended for piracy. Moreover, its easy to see how such a device is parasitic on the platform itself, so that if Nintendo didn't do something about it then there won't be a Nintendo.)
If the later is not allowed, this very comment might be illegal, as I'm telling you that such a thing is possible.
Nintendo has previously sued a company for selling a device which allows people to mod the device they owned. https://en.m.wikipedia.org/wiki/Lewis_Galoob_Toys,_Inc._v._N.... Nintendo is notoriously anti-consumer in this regard.
And anyways, restricting mods is unnecessary to encourage the economic viability of video games.
Interviewing family members, hiring someone to build a schedule of your coming and goings, and so on... Does not seem like a "soft touch" approach to me. To be frank, it's something I would expect of the Yakuza, not a game company.
iFixit is safe because it doesn't really affect Apple's sales. It may put a slightly downward pressure on Apple Store repair revenue. But iFixit solutions require technical aptitude, time and skill to apply that most people don't have, and wouldn't spend on fixing a laptop even if they had it!
But what if iFixit sold a dohicky that defeats the copy protection on all software written for macOS? Do you think that's okay, and that their right to share that device is free speech?
The issue I have is that they target people who figure out how to run and copy cracked game from their device, and not those who are actively distributing them. While it makes perfect sense from their side, the images from the tweet feed do not present a compelling argument that the modders are breaking the law and as such they are intimidating law-abiding citizen which is horrifying.
That's all that matters.
Interestingly, Nintendo's explicit message was not that the hacking was wrong, but that the sharing of the hacking was wrong, because sharing the hack encourages piracy on a larger scale. It's hard to argue with that logic, TBH. And I actually admire their soft touch approach.
My sense is that this is not that big of a deal, to Nintendo or anyone else. The platform, the physicality of "normal" distribution, plus the general inability of people to successfully mod their stuff, all favors Nintendo naturally.
Seems like a tempest in a teapot, and if anything, I don't think it harms Nintendo's reputation at all (modulo sensationalist headlines).