I had a copy of 'Os Lusiadas' (the epic poem written by the Portuguese Camões), with a preface written by a contemporary (XVI century) bishop. 

I do not remember the exact words, by the general idea was: "I must inform the reader that the book deals with the ancient pagan religion of Rome and its deities, and in many instances, it is written as if they were true. But as it is not expected that anybody takes this seriously, nor there are any true followers of this old religion which might tempt a christian, it is not a threat to anybody's faith. Besides that, we may also find similar literary forms related to the roman deities in the old Roman classics which we all enjoy."

see, people were smart back there, too. I also guess people never stopped reading classics such as the Odyssey or the Iliad. If you tell teenagers to read Homer, what would be the reason of objecting to a painting of a deity?