It is better to be hot or cold, rather than lukewarm.
Other than that, I dispute the underlying tenor of the article.
In my experience, those who commend others on doubting their faith are themselves (so-called) progressives.
That is the sort of sophistry I have heard from devotees of Fuller Heresy Factory (”A true faith is a doubting faith,” as one such told me), going back decades.
Joshua Harris was a legalist, which is why I rejected his ostensible ministry when I first encountered it; he was a modern-day Bill Gothard, whose ministry I also rejected in the early 1970s (although it took decades for the corruption in his organization to come to light).
He then went on to become a full-blown heretic. I am not going to commend someone who created a ministry to satisfy his ego, so that he could mislead thousands of people for many years.
Biblical morality and sanctification are hardly admonished from the pulpit today. It was because I was looking for such that I discovered his book on dating. However, a cursory perusal quickly convinced me it was not in fact Biblical.
Bottom line: Joshua Harris was a false teacher who abused and then betrayed people who regrettably followed his leading.
You are quite right....and so many “Christian” leaders in the homeschool world were super legalistic, which is as you note, inherently abusive (not to mention false).