I want to know the answer to the following question:
For what purpose did detractors use the idea of Mary's virginity and the virgin conception of Jesus?
All the background I'm provided with is that "In the 2nd century, as part of the earliest anti-Christian polemics, Celsus suggested that Jesus was the illegitimate son of a Roman soldier named Panthera.". Is that enough to answer the question?
Answer: no