I get that argument, but I'm not sure you have the relative population sizes right. It seems a bit doubtful that millions of MSI users are interested in flashing custom firmware on their motherboards, but every user is potentially impacted by signed malware. Particularly since the firmware signing is a known thing and there's less restricted hardware available. People really interested in being able to do whatever they want with their hardware are presumably purchasing accordingly.
Like I said, I get the support for increased openness and freedom in hardware and the appeal that has to some users. But security is a feature that a lot of users (even power users) care about too, and it's bad when that feature breaks.
