One thing I've realized in the course of my conversations and friendships with other Catholics is that some people treat the Brown Scapular (which I wear faithfully myself) as a sort of talisman to protect them and their children from all evil.
A close friend of mine told me recently that her Mom was encouraging her to have her children enrolled in the Brown Scapular because of the protection it would offer. Her answer was that no, her Mom had made her and siblings wear the scapular growing up and it never protected them from the evils of their abusive father.
There are multiple layers of evil that come out of treating the scapular as a talisman or presuming that it will protect the wearer from all harm...
1. The scandal it creates, especially for those who might already tend to think of legitimate Catholic practices as superstitious.
2. The negative association that can develop around this legitimate and worthwhile devotion.
3. The possibility of falling into serious sin by presuming that the scapular will protect you from all evils. Remember that we are supposed to "avoid the near occasion of sin" - there's nothing about this point being moot when we're wearing our scapular.
The devil loves to help confuse and twist even the most beautiful of legitimate devotions.
St. Thomas Aquinas teaches that virtues can be understood as a "means" or "middle ground" between two vices. For example, courage falls somewhere in-between cowardice and rashness. The "extremes" of the virtue of Hope would be despair and presumption.
Some further reading on the Brown Scapular and Catholic teaching on presumption:
The Brown Scapular - EWTN
The Brown Scapular - Las Vegas Marian Center
Catholic Encyclopedia: The Deadly Sins of Presumption and Despair
Garment of Grace: A Historical Appreciation of the Carmelite Scapular