That'd be very bad and short sighted advice. Smart taking 3's MIGHT cost us a game here or there in the short-term, but that's a very small price to pay for his potential development into a solid 3 point shooter. Imagine if the Celtics told Jae Crowder (which would've been more logical than doing so with Smart---not that I wanted us to tell Crowder that either), who was 24 years old and shot 29.3% from 3 last year, to stop taking 3's. A year later at 25 years old he is hitting 36.7% of his 3's while taking more than ever before.
Olynyk, while not in that Smart or Crowder poor 3 point % range, has also shown massive improvement in his shooting in his age 24 season. These things take time.
Smart shot 33.5% as a 20 year old rookie from 3. His regression there has been a disappointment for sure, but we are years and years away from the point of telling him to stop taking 3's. He's way too young for that, and he actually showed potential from 3 just a year ago. He needs to cut out some of the really crazy, really dumb ones that he throws up on occasion. But that's it...