If you’re using antivirus software, of course you only want it to warn you if there is really a virus.
Warnings about viruses-that-are-not-really-viruses are called false positives.
It goes without saying that antivirus software that reports false positives is bad software.
Read below what The Register wrote on a recent false positive, detected by McAfee.
This is, of course, one of the many reasons why one shouldn’t use this inferior product: