Ours is currently ~5 - 6". He is actually one of the most calm fish we have, until the lights go out, then he is darting around, swimming in and out of the rocks, weaving through all the plants etc.
In the time we have have had him, we have not seen him chasing or "nipping" at the others in the tank. As I said, he hangs out with the 6 cory cats we have. Feeding him is a blast, he starts from the bottom rushes to the top, grabs whatever he is going for and rushes back down, all in milliseconds, if the hood is open when he does, be ready for a wave of water lol.
He also seems to know when I am around the tank because comes out near glass and follows me back and forth, does not do this with anyone else in the house. I am looking into a 135 gallon tank here locally, may pick it up and get 3 - 4 more and devote a tank to just him and his buddies, I feel bad that he was the only one, unfortunately he was the only one in the tank when I purchased him, so I only got the one. I hope he is not getting confused about what he is, since he hangs with the cory cats...
I do not believe he / she is trying to be rude. He is simply stating that the fish himself would be happier in a larger tank. Even being small, he still has requirements for swimming around, territories etc. While the bala may "fit" in the 10 gallon tank, it is not his optimal placement, especially for extended periods of time like a few months. They are just letting you know that his current conditions do not fit his needs, no one is trying to be mean or rude, just giving you the information, especially since you were misinformed regarding how large they grow etc.