There's a place for discernment ministries, especially now, with so much apostasy and false teaching going 'round. Discernment is a spiritual gift for the building up of the saints, like any other gift. But we have to test the spirits of the discerners as well. Just because someone has a discernment ministry that doesn't mean they should be trusted.
In my experience, those who cry the most loudly against discernment ministries do so because they have something invested in what is being exposed, and therefore something to lose.
Okay...
But you are wrong. There was lots of these false doctrines almost immediately after the Early Church was started and began to spread.
And the way to combat the false doctrines has been laid out clearly already...not by finger pointing but by telling how good and real God is as well as explaining what Holy lifestyles are point by point in opposition to the heresies.
None of us are truly blameless. There are none righteous, no not one. Even the best amongst us doing their most righteous acts are as feces in a cesspool.
It's a target rich environment.
We are only blameless because of Jesus...what God wants from us is clearly laid out in scripture...both in the Old and New testaments. And it hasn't really changed.
Walking humbly with God is not in alignment with slandering others. Even if it is true.