Thousands of blacks fought for the South in the Civil War. This is evidenced by Pension rolls in many Southern States. These blacks were not forced to do so (even the article you linked above does not make this claim about Silas). Many of the blacks either fought because of personal convictions (like entire regiments of Zouave from New Orleans fought for the South while the First Louisiana fought for the North). Others fought out of devotion to their masters. The majority of blacks in the Southern army served in non-combatant roles such as transport handlers. There were few if any instances of any black being forced to serve the South. Is it fair to say that many blacks who served the South were not fully aware of the issues being decided by the war in full context? Yes. However nearly all were volunteers.
Yes there were some blacks that supported the confederacy(mostly slaves) just as there are some blacks that support the republican party today.In both cases its a small percentage.