Can any piece of artwork ever be bad if it stems from real emotion that the artist feels?

Yes! Even if we agreed that a 'real emotion' was a necessary feature of all art (and that's a big 'if'), it might not be the only feature. For example, the emotion would still need to be well expressed or communicated; the product might need to avoid being banal or commonplace; we might think it needs also to show or teach us something. I would like to add that, supposing art does have something to do with emotion, there is still much to recommend Wordsworth's notion that poetry at least should have its origin in 'emotion recollected in tranquility'.