Yea but if I am the exception then you may have discouraged and prevented me from succeeding. If not, not much harm done right? All for what, so you can say I told you so 99% of the time?
If a comment like that can discourage you, you are not ready. It's like starting to train for a marathon and quickly forgetting the idea because you don't like your shoes, or something equally trivial.
If you think I exaggerate, try staying focused on your startup after months of investor rejection (which is the norm, by the way).
Yes it can discourage someone, especially if it adds up. My point is that it doesn't really help anyone. You're not doing anyone any favors letting them know a couple months ahead of time their chances are slim. They'll find out themselves if they're the 1% or 99%.
