Most of what was said about Muaawiya either a lie fabricated by his rivals or anti Ummayad, or propaganda paid by his dynasty.
This narration is in Tafsir Ibn Kathir.
Do you think Ibn Kathir was an enemy of Muawiyah and the Umayyads?
Ibn Kathir is considered a member of the Umayyad party and was not an enemy of Muawiyah the Umayyad.
تفسير ابن كثير
وَلَا تَنكِحُوا مَا نَكَحَ آبَاؤُكُم مِّنَ النِّسَاءِ إِلَّا مَا قَدْ سَلَفَ ۚ إِنَّهُ كَانَ فَاحِشَةً وَمَقْتًا وَسَاءَ سَبِيلًا (22)
وقد أجمع العلماء على تحريم من وطئها الأب بتزويج أو ملك أو بشبهة أيضا ، واختلفوا فيمن باشرها بشهوة دون الجماع ، أو نظر إلى ما لا يحل له النظر إليه منها لو كانت أجنبية . فعن الإمام أحمد رحمه الله أنها تحرم أيضا بذلك . قد روى [ الحافظ ] ابن عساكر في ترجمة خديج الحصني مولى معاوية قال : اشترى لمعاوية جارية بيضاء جميلة ، فأدخلها عليه مجردة وبيده قضيب . فجعل يهوي به إلى متاعها ويقول : هذا المتاع لو كان له متاع! اذهب بها إلى يزيد بن معاوية . ثم قال : لا ادع لي ربيعة بن عمرو الجرشي - وكان فقيها - فلما دخل عليه قال : إن هذه أتيت بها مجردة ، فرأيت منها ذاك وذاك ، وإني أردت أن أبعث بها إلى يزيد . فقال : لا تفعل يا أمير المؤمنين ، فإنها لا تصلح له . ثم قال : نعم ما رأيت . ثم قال : ادع لي عبد الله بن مسعدة الفزاري ، فدعوته ، وكان آدم شديد الأدمة ، فقال : دونك هذه ، بيض بها ولدك . قال : و [ قد ] كان عبد الله بن مسعدة هذا وهبه رسول الله صلى الله عليه وسلم لابنته فاطمة فربته ثم أعتقته ثم كان بعد ذلك مع معاوية من الناس على علي [ بن أبي طالب ] رضي الله عنه
The scholars have unanimously agreed that it is forbidden to have intercourse with a woman with whom the father has intercourse through marriage, possession, or suspicion as well, and they differed regarding someone who has intercourse with her with desire rather than intercourse, or who looks at what it is not permissible for him to look at from her if she were a foreigner. On the authority of Imam Ahmad, may God have mercy on him, it is also forbidden in this way.
[Al-Hafiz] Ibn Asakir narrated in the biography of Khadij Al-Husni, a freed slave of Muawiyah, who said: They bought a beautiful white slave girl for Muawiyah and he brought her to him naked, with a penis in his hand.
So he started to lean towards ( his penis ) to her ( private part ) and : Then he lowered his penis into her vagina! and he said take her to Yazid bin Muawiyah. Then he said: Do invite Rabi’ah bin Amr al-Jarashi - who was a jurist - to me.
When he entered upon him, he said: I came to this ( white slave girl ) naked , and I saw this and that from her, and I wanted to send it to Yazid ( Muawiyah's son ).
He ( Rabi’ah bin Amr al-Jarashi ) said: Do not do that, O Commander of the Faithful
( Muawiyah ), for it is not suitable for him. Then he ( Muawiyah ) said: Yes, That is the best of your opinion.
Then he said: Call Abdullah bin Masada Al-Fazari for me, so I called him, he was
Aadam Shadeed Al Udmah (
very dark black ), so he said: take this ( the white slave girl ) , And to make your offspring white ( whitewash your offspring by sleeping to the white slave girl ) .
He ( Muawiyah ) said : And [this] was Abdullah bin Masada, whom the Messenger of God, may God bless him and grant him peace, granted ( Abdullah bin Masada as slave ) to his daughter Fatima, who raised him and then freed him, and after that he was with Muawiyah among the people over Ali [bin Abi Talib], may God be pleased with him.