Is reviling Bani Hashim considered apostasy? Is preferring one tribe over Quraish considered apostasy? And what are the reasons for neglecting the rights of the Prophet's Household in this era, and why isn't the public made aware of the belief in their veneration and allegiance?

Merely cursing the Banu Hashim does not constitute disbelief (kufr), unless the curser intends to curse the Prophet (peace be upon him). However, one who utters such an abominable statement should be disciplined and punished. If a Hashemite says, "May Allah curse Banu Hashim," and intends thereby the unjust among them, or if he utters an abominable statement about the forefathers or descendants of someone he knows to be from the Prophet's progeny (peace be upon him), then this phrasing could imply a general curse. While the curse might be intended specifically for the unjust, it is more appropriate to consider it as an absolute statement, with severe disciplinary measures for the one who utters it.