Question

Why can DNA profiling be bad?

Answer 1

DNA testing and profiling isn't perfect

Explanation:

To begin with it's not foolproof or perfect. When DNA analysis goes wrong, people can be told they are a parent, or put in jail, or told their predisposed to a condition or disease that they aren't. DNA can also be generated. If real DNA is found at a crime scene then great! Unless it's fabricated in a lab. Then you have a problem.

( There's also a privacy issue. For DNA to be matched a sample must be compared to a database, and dome people are weary of DNA databases. In medicine people worry that having their genetic code, and thus possible disposition towards certain cancers or genetic diseases on record could result in being made to pay more for medicines and insurance. )
It's mostly the first thing, though about profiling not always working.