You can argue current-gen emulators are irresponsible, you can say they're mostly used for piracy, but Nintendo doesn't have a right to stop people from talking about emulators. Taking down videos that talk about emulators is not Nintendo protecting its IP, it is an abuse of the DMCA or other non-DMCA tools in Youtube to shut down conversation that Nintendo has no legal right to shut down. Nintendo does not have the legal right to demand people not talk about emulators or share how they work, that's not a right that IP law grants. To say that they're protecting their IP is just false, they're claiming IP rights that they don't have.
Of course in this scenario, no one is going to challenge these takedowns because no one wants to get sued, and the stakes are ultimately unbelievably low. But a video about how to install an emulator is probably not copyright infringement, and (IANAL), I would be very surprised to see Nintendo get a positive ruling if they actually sued someone over showing how to install an emulator on a computer. Again, IANAL, but I'm not even sure you would claim fair use in a case like this. Fair use is a defense for violating copyright, and emulators don't violate copyright.
Discussions about the morality of emulation and the proliferation of piracy are fine, this can be a complicated subject with moral ramifications. But legally speaking, at least in the US, emulators are not piracy and talking about them is not copyright infringement.