How much more blatant does the guy have to be to be proven as a member of the evil organization? He quite literally just sent the gestapo down to crush a bunch of farmers and force them back into what is basically slavery.
I wonder how Mephisto will react to this situation, let alone if Iruma and his allies will actually come to blows with this Fang group. These guys already are openly attacking children and old people, let alone inadvertently attacking Iruma, so I'll be shocked if they don't try to fight somehow unless the power difference is truly that one-sided.
Edit: Now that I think about it, this is also going to piss off Asmodeus' family to a rather extreme degree since it would directly put them against her newfound ambitions with the restaurant and carrot deal. So we have at least one, if not two, of the 13 crowns that are invested in the same ground this guy just laid claim to.