What bad behavior did Rousseau learn from his apprenticeship with M. Ducommun; what is Rousseau arguing here?

Abel Ducommun was
an engraver in Geneva to whom Rousseau was apprenticed in 1725. The choice was not a positive
one, as the engraver is described as violent and as incapable of developing a positive
relationship with Jean Jacques. He often punished his apprentice and his violent behavior
eventually led Rousseau to escape from Geneva. Therefore Ducommun was a negative teacher for
Jean Jacques as he taught him to be violent and, with himdsight, the author holds him
responsible for his own moral degradation. The character of Ducommun proves Rousseau's ideas on
the corrupting effects of society: although he is originally from a good family, Ducommun goes
through quick decay and dies in poverty.