The son's DNA was not good enough to convict the father. The son's DNA was good enough to lead police to investigate the family which lead to the arrest of the father.
The problem regarding race that the article mentions is simply one of social statistics: if 10x more convictions per 1k convictions occur for group A than group B and we assume convictions are familially independent (close enough), people in group A are 10x more likely to be suspected of a crime via familial inference than those in group B.
It's not quite racial profiling but it does imply that you have fewer rights as a genetic relative of a convict than as a non-relative. That's somewhat disturbing.