Abba_S: I would like to apologize if I came across too harshly. It is just that I get very upset when people spread Motzi Shem Ra or Loshon Hora about others, but I should express myself less harshly, and I am working on that.
I would also like to clarify the issue. Motzi Shem Ra refers to saying something that is both untrue (which includes anything that is not definitely known to be true) and negative. It is assur to say Motzi Shem Ra even for a toeles.
Saying that this guy is not dating for marriage is a negative statement and untrue (since you have no way of knowing if it is true or not). Therefore it is Motzi Shem Ra and it is assur to say it even for toeles.