Merriam Online Dictionary
Definition of a RUMOR:
1: talk or opinion widely disseminated with no discernible source
2: a statement or report current without known authority for its truth
3: archaic : talk or report of a notable person or event
4: a soft low indistinct sound : murmur
There is NOTHING wrong with a rumor of and by itself; it's only when people carelessly slander others with a rumor and all without any proof that it's wrong. Saying negative things that could damage a person's reputation or business, without proof, is one thing, but simply repeating an unproven idea or statement is another thing.
If I stated that I heard that someone in these forums really loved pizza, it might be just a rumor but it's not necessarily evil even if I'm wrong and they don't like pizza. Loving or hating pizza is neither wrong nor is it right. However, if, on the other hand, I say that I heard a rumor that the same person in question loves to take illegal drugs, or engage in illegal porn, etc., that is totally wrong and would be subject to the laws of the land. Of course, if you could prove that was all true then it wouldn't be a rumor but a fact. Like anything, a rumor can be innocent or far from it; a rumor can be good or it can be bad, but let's don't go around trying to curb free speech based on the fact that some rumors are wrong. In other words: don't throw the baby out with the bath water.