You may feel loyal to him, especially if he is a close friend or a relative. But if you were to cover up the wrongdoing, you would be disloyal to God.
يُسَاعِدُكَ ٱللُّطْفُ أَنْ تُوَفِّقَ بَيْنَ وَلَائِكَ لِيَهْوَهَ وَوَلَائِكَ لِلْآخَرِينَ .‏