The FSF openly endorses devices with hundreds of kilobytes of nonfree blobs burned into ROM. They do this because they claim they can just "say it's equivalent to hardware". They only care about blobs when they're loaded from software, because at that point their existence becomes apparent, even though naturally a blob loaded into RAM gives the user more freedom (e.g. to inspect it or change it) than a blob loaded from ROM.
your statement is misleading
why did you add "unless you can't see them"
did FSF said binary blobs you can't see are not bad? Seems opposite from what FSF would do