Some are good in spite of Islam, not because of it. The life that the fake prophet led is of primary importance as they consider him the perfect man and so follow his example, that example is immoral, violent and oppressive.
No matter how many good muslims there are does not alter any of the evil in the Quran any more than good Nazis or communists justified or changed what they believed in. Islam is supremacist, intolerant and always potentially violent, there may be moderate muslims, there is no moderate Islam.