Is the word "Istishraf" (anticipation/foresight) – used to describe those who demand and defend virtue, and criticize those who fight it, but in a negative sense that implies hypocrisy – considered a term of slander, and what are the implications of that, and what if the people of the country were described by it?

The slander (qadhf) that necessitates the ḥadd punishment is when a responsible, free, Muslim, sane, chaste person accuses someone of denying paternity or of committing zinā (unlawful sexual intercourse). The expressions of slander are divided into explicit, implicit, and insinuating. The statement mentioned in the question is not considered explicit, implicit, or insinuating slander, whether directed at an individual or at the people of a country. If one slanders the people of a country, it is inconceivable that all of them would have committed zinā, so no ḥadd punishment applies to him; rather, he is subject to taʿzīr (discretionary punishment). This statement is considered a forbidden insult in Islamic law, and its punishment is taʿzīr.