What is the ruling on a father or mother saying to their son, concerning a poor person or someone in a profession that is looked down upon, "Study hard so you don't end up like him," if this is said by way of disdain for the person or their profession?

The apparent meaning of the phrase is to advise the son to diligently pursue his studies to secure good jobs, and not to neglect them, so as to avoid being compelled to work in lowly professions. There is no religious prohibition against this, as professions vary. Nevertheless, it is not permissible to belittle those who work in such professions or any others, for belittling a Muslim is religiously forbidden.