Islam is a large structure that combines many different aspects of human life and such a structure requires a foundation and pillars that it rests upon.
Tawheed is to single out Allah (Exalted be He) in what is distinct to Him and obligatory for Him. That is, for the slave to know for certain that Allah is One with no partner.
Can attacking the places of worship, i.e. churches, be justified in any religious teachings including Islamic? What does Islam say and teach about that? How can a religion be judged correctly?
The story of Bilal teach us the true meaning of freedom, that blackness of skin and bondage would not decry the greatness of the soul if it found its faith, adhered to its Creator, and clung to its right.