[Rusty]

Glad you disagreed. I forced English grammar on the verb creer!
Sorry about the confusion.

To wrap our English-wired heads around the Spanish indirect object used in creer algo a alguien, we need to insert words to make it work.

- Juan te está mintiendo; no le creas.
- John is lying to you; don't believe (it-mandatory English direct object pronoun, not necessary in Spanish) (of) him.

- Los niños dicen que tú les diste dulces; no les creo.
- The children say you gave them some candy; I don't believe (it-mandatory English direct object pronoun) (of) them.
-or- I don't believe (them when they say) (it-mandatory English direct object: (that) you gave them some candy).