Ionia is Greece, inhabited in ancient times by the Greeks, the Ionians.  

"The Ionians" founded the first ancient Greek school of science and philosophy.

(Through Ionia there were lively trade routes and cultural connections with various countries.)

"Ionia" is an image of Greek, pagan philosophy, culture, religions, and all their representatives, against which the Wisdom of God's Will - the opposite of the wisdom of the sinful world - was opposed.

"Sons of Ionia" is an image, a characteristic of people born, brought up by a sinful system, nurtured by various "pagan," sinful ideologies, beliefs, philosophies.