User blog comment:Fintin/Who's the real antagonist?/@comment-7764547-20130411190933/@comment-4820500-20130412051258

while its  not stated in that they are, it is strongly implied in that the BB pirates are very similar to the SH in beliefs and skills but an evil version of it. Also since they have been present pretty much since the SH got on the grand line but have yet to officially meet crew to crew  implies that they have a great significance to the story