"Cult" is best reserved for it's traditional meaning, which is a way of referring to a particular devotion or practice within a religion, for example the cult of a specific saint within Catholicism or Sufi Islam.

When used as a way of referring to a religion it is generally understood as intended to insult. Generally that seems to be the intention. Not to exaggerate, but it's an expression of the same mindset that gives rise to persecution.