Fun Fact: If you were to rip a Bluray to your computer, you’re legally not permitted to watch that movie if you’re no longer in possession of the disc.
Not sure why you think this.
You can legally rip a Bluray for backup purposes. If you sell or give away the Bluray, you have to delete the backed up copy. If it’s lost, stolen, or unintentionally damaged, you do not.
However, you cannot bypass the DRM to watch it or when you’re creating the backup. This is true regardless of whether you still possess the physical disc.
Decrypting DRM is illegal not based on whether you own the content but because the DRM encryption itself is separately copyright protected.
Bypassing DRM is illegal because the DMCA explicitly prohibits the circumvention of technological measures that control access to copyrighted works, and there isn’t an exemption for personal use, personal backups, or fair use in general.
It doesn’t matter if it’s emulated legally or not. They can issue a takedown for showing gameplay captured from an NES hooked up to a CRT if they want.
A fair use defense has to be defended in court, and it’s not just about whether you’re right but also about whether you can afford to fight.
It’s also not certain that a fair use defense would fly. One of the elements for determining whether fair use is market impact, and I suspect that Nintendo’s lawyers would argue that demoing that their games can be emulated - even if the specific demoed games are not being sold - has a negative market impact, since it makes people who might buy a Switch and a Nintendo Online membership to play the official emulated games less likely to do so.