Truth Will Set You Free
I guess that I agree with this if it's a tournament, gambling, or a league match. But I've had friends want to beat me so bad when just playing for fun, that they do this then. I mean, for a practice game, I'm pretty sure that I'm telling my opponent that he's shooting at the wrong ball. But if it's the guy that just did that to me in the previous practice game, maybe I wouldn't then either. LOLI remember more than a few years ago we had a thread similar to this one. I also remember that in that thread I commented that unless I absolutely detested my opponent, I would surely warn him if he/she were about to shoot the wrong ball.
I have since changed my mind.
After literally years of watching underrated players getting spots and winning without the spot, players doing all kinds of subtle sharking, players paying more attention to their cell phones than they are their game, etc., I am at the point where I will try to win the game in whatever way I can do it within the rules.
Last I checked, there were no rules for warning your opponent that they are shooting at the wrong ball. And the posters that say "it's on them" are absolutely correct.