Yes it's bad to wear a Rosary around your neck even if you happen to be catholic.
Some people who do wear a Rosary around their neck do so because they believe that the Rosary provides a blessing or protection but it's just a superstition.
The Rosary contains no magic abilities and is wrong to wear the Rosary around your neck no matter what.
Rosaries are not intended to be worn as Jewelry and it's inappropriate to wear Rosaries around your neck.