A Worker/Writer is Worthy of his Pay
Getting paid for your writing effort isn't bad. It is expected that now or later you will get paid for your labors. 1 Timothy 5:18 KJV (For the scripture saith, Thou shalt not muzzle the ox that treadeth out the corn. And, The labourer [is] worthy of his reward. ) A problem occurs when your misuse of a writing gift creates a negative or harmful result. For example, if you have a gift of writing and decide to write material that leads another to sin, isn't your writing creating a stumbling block for others? Romans 14:13 KJV (Let us not therefore judge one another any more: but judge this rather, that no man put a stumbling block or an occasion to fall in [his] brother's way.)
You can write a story for the right reason, but deliver it in the wrong manner. As Nissa pointed out in her comment, a preachy, negative tone gets in the way of a story. What is your reason for writing the story? Is it a sincere attempt to aid others through your writing, or are you using the story as a soapbox to pound someone over the head until a desired belief is accepted? Fictional stories can contain a theme and a message. A story shouted too loudlyat the reader to persuade them of a certain view may prevent the reader from staying to hear either the theme or the message because they have already closed the book.