Why does street names for Heroin make it sound less dangerous?

Such as big H, blacktar, brown sugar, dope, horse, junk, mud, skag and most common, smack. After September 11th, heroin was even called Bin Laden, twin towers and WTC. Some other interesting street names are Bart Simpson, Aunt Hazel, birdie powder, Dr. Feelgood, dog food, hong-yen, lemonade, Mexican mud etc.