Religious subjects are suitable topics for the arts because there are many aspects of religion that is intertwined with art. Although I do not believe that the arts, in general, should promote religion, but I do believe it should discuss it when it relates to the piece of art. If it helps to understand the art then it should be discussed.
Religious topics are largely considered an artistic topic. This is why I believe that they are acceptable and suitable topics for the various Arts communities to be discussed. Different religions and themes in religions can add harmony to the Arts community when it is discussed in any length of amount.