I seriously don't get why you'd even care about the distinction. For the same reason we don't distinguish between specific models/versions of armament, we shouldn't really care about bass vs. guitar. They look the same and it's danbooru, not instrumentbooru. If you really need, you can make bass imply guitar, but don't untag pics.
Technically, this isn't a bass, it's a bass guitar. There isn't really such an instrument as a bass, the only bass is a type of fish. Of course, "bass" is used to refer to a variety of instruments since it's annoying to say "double bass" or "bass guitar", but if you want to nitpick, you better be correct.
Tagging this instrument as "bass" and "guitar" makes the most sense to me. (Implying it sounds like a bad idea to me though, there are a lot of basses that aren't guitars.)
Well to be pedantic, it's not the "bass type of the guitar family" it's actually the "guitar type of the bass family", that is to say that "bass" is a grouping of instruments in itself. However, so it guitar. Therefore it's totally splitting hairs to really make a fuss about it.
