In my 50 years as a JW, I never saw any time that Shunning was a "positive" thing.
Though I do know of 2 people who were shunned due to addictions (one was for smoking, one for drinking).
The shunning by their friends and family worked great! It crushed their world, and at a time they needed family more than ever, they both (in different decades) chose suicide to cope with their pain.