"He claimed to be a Christian, but by his deeds he has suggested otherwise," Michael writes in the lengthy essay posted on Monday. "It distresses me to say that Josh Duggar's greatest sin is a byproduct of the sum total of his secretly sinful lifestyle. That is, that by his hypocrisy, he blasphemed the name of God."
He goes on to slam Josh's "lifestyle of evil," while at the same time publicly professing Christian values.
"With the name of God on his lips he lived a covert and extensive lifestyle of evil," Michael continues. "While proudly saying things like, 'Our family is like the epitome of conservative values,' he was looking at porn and soliciting affairs. He took a job at the Family Research Council that exists to promote the traditional family, all the while undermining his own family by violating his marriage covenant. He flourished in the fame of his family and the success of their television show, all the while betraying their trust and Christian values."
Still, Michael says Josh "brought shame" upon the Christian faith.
"The thing that is so hurtful is that he was a loud voice endorsing Christian ethics and he has been shown to be a fraud," he explains. "I am profoundly grieved that he attained such a platform only to bring shame on God's holy name and the Christian faith."
"Josh was a pretender," he writes bluntly. "True Christians fail often, but their lives are truly being conformed to the image of Christ. Do not look at Josh and justify your own sins by dismissing the reality of genuine faith and a holy God."
Ben Seewald's father notes he feels "deceived" by Josh, after standing by him following his admission in May that he molested five girls as a teenager -- four of whom were his younger sisters. Clearly, he is no longer supporting him.
"Sadly, he had deceived us all," Michael writes. "The name of God has been blasphemed and God is jealous for his name."