Imaculata
Hero
Yeah, I agree with @Retreater on this one and your DM, but I also see the other point of view.
The spell affects a single target. The DM could easily rule that target gets advantage because it knows following your suggestion will put it at odds with the other cultists anyway.
That is not how the spell works. The spell makes the target ignore such details. This was a reasonable request that would not result in any direct harm to the target. So at the very least this could have resulted in a conflict between the leader and the other cultists.