When a Christian brother is caught in sin, the "goal" is restoration (Gal. 6:1), not as you framed it -- a "takedown." And Paul also reminds there to watch it ourselves, lest we, too, fall. We know that if we've escaped sin, there's nothing to "boast" about there (Eph. 2:8-9) in Him saving us. We know that we can't take pride in our own accomplishments: Pride goeth before destruction, and an haughty spirit before a fall. (Prov. 16:18)
Now why doesn't this work very easily in Mormonism?
(1) Because we're not simply talking about a single sin: The Mormon "prophet" has declared that if you repeat a sin you've repented of before, you weren't genuine in your repentence to begin with...therefore your "religious" life has been a sham all along. The sin, per Mormonism, just reveals sham religiosity.
(2) When Scripture says "be perfect" (Matt. 5:48), they expect that's what it means to be part of godhood. They expect to be perfect. And Kimball the "prophet" has said that Mormon men can pick themselves up by their own bootstraps.
Hence, Mormons have erected a tremendously sky high Tower of Babel of righteousness. They are building their own way to heaven via their own self-righteousness. Therefore, when Mormonism displays a track record pretty much "on keel" with the world criminal behavior wise, it shows cracks in the Tower of Babel self-righteousness foundation. They are not the gods-in-embryo they pretend to be.
Look at me, Im Colofornian. I can copy and paste and write really long responses without actually addressing anything anyone said. I can also make it ok to bad mouth one religion while at the same time make it verboten to bad mouth another, I must be related to Jesus or something :)