This claim is not true, but evil is evil, whether one is from the first or later generations (who embraced Islam), a ruler or otherwise. And good is good, whether one is from the first or later generations. Time has nothing to do with the character of the person, his piety or immorality.
The Awliya’ of Allah are the people of Iman (Faith) and Taqwa (fear/wariness of offending Allah). Allah says (what means):
No doubt! Verily, the Auliyâ’ of Allâh [i.e. those who believe in the Oneness of Allâh and fear Allâh much (abstain from all kinds of sins and evil deeds which he has forbidden), and love Allâh much (perform all kinds of good deeds which He has ordained)], no fear shall come upon them nor shall they grieve.
Those who believed (in the Oneness of Allâh - Islâmic Monotheism), and used to fear Allâh much (by abstaining from evil deeds and sins and by doing righteous deeds).
(Surah Yunus, 10: 62-63).May Allah grant us success. May peace and blessings be upon our Prophet Muhammad, his family, and Companions.