theres many reasons
for one; boogiepop = a fictional being in reality, but also is thought to be fictional in the boogieverse, but actually exists in the boogieverse, however "it" is borne from humanity
now in retrospect to Wagner's Die Meistersinger von Nürnberg...its the only story he wrote which actually had a realistic setting (as opposed to a faerie land or something like that), much like the boogieverse.
now also the main character in this play is a "behind the scenes" character until pretty much the end of the play, where his true nature is revealed (as a true maestro of music and such), and after this he has the power and position to change music as it is, but he finds beauty in all music, and thus intends to preserve music no matter the origin or form.
for boogie this is the case in respect to humans, he CAN wipe them all out, or wipe out the ones he doesnt like, but instead he acts to "preserve" existence, from behind the scenes.