If you only have what it takes to butcher music, then stop.
Classical music clearly isn't the most popular in the world at present. This is no longer the day of Mozart and bourgeois salons. Classical music is more of a niche endeavor than a mainstream one, and elitist statements like this one could rightly be one of the causes.
No, most people with an interest in the piano are not at the level of Horowitz, Rubinstein - few are in fact. Yes, to people with the highest level of training, someone who is just starting out could be considered an annoying and incompetent juvenile, however it's really a matter of perspective. I have a feeling, Thierry, that Mozart or Beethoven would consider you the same, even if you have trained at the best conservatories.
This kind of rude elitism is one of the reasons that classical music is not accepted in the mainstream. People who have a genuine love for the piano, or any classical instrument, but lack the training are often ridiculed and teased. It makes perfect sense to me that they would reject the artform in it's entirety, if nothing else than to avoid the pompous exclusivity with which it reeks.
As someone who loves classical music, particularly at the highest level of performance, I understand the desire to have the works of the great composers played at the most elevated level, however there are few in this world who can do their works justice, and once one starts down the slippery slope of deciding who can and who cannot make music, there is no return.
It would be far more constructive to attempt to educate newly interested enthusiasts towards a better approach than to suggest that they quit entirely. One must remember as well, that even the greats of the piano had to start at the beginning. If everyone who played at a mediocre or poor level were to stop today, there would very little classical music left in the world.
Classical music is on the decline and the vast majority of people in the world can name more Britney Spears songs than they can Beethoven symphonies, even considering the fact that the latter are numbered. Condescending and arrogant attitudes from more accomplished classical musicians will not help this cause at all.