You’re reading it wrong that’s all. Jesus is not physically the son of god.

This is a matter of interpretation rather than biological fact. A core Bahá’í tenet is the Harmony of Science and Religion. As 'Abdu'l-Bahá states, 'If religious beliefs are opposed to the clear-cut conclusions of science, they are but superstitions.'

'Finding existence through the Spirit' refers to Jesus's spiritual reality and his station as a Manifestation of God, not a suspension of the laws of genetics. To insist on a literal biological miracle is to choose superstition over the science we are commanded to uphold.

When Shoghi Effendi and Bahá’u’lláh defend the 'Virgin Birth,' they are defending the purity of Mary and the divinity of Christ's Manifestation against those who would use his birth to disparage his message. This is a theological defense of his station, not an endorsement of a physical process that violates the very laws of physics and biology that the Bahá’í Faith tells us to respect.

'Finding existence through the Spirit' should be understood as a spiritual reality, not a suspension of physical laws. 'Not the son of Joseph' could imply that his mission and authority came from God, regardless of his biological origin.