There is a very interesting post written by @TechZen. Here's the excerpt from the original post (bold emphasis mine) Should I get an antivirus for my Mac?
There's never been a an actual Mac OS X or iOS virus in the wild that infected any end user's computer. Viruses are malware that can auto replicate without human interaction. All the malware listed in the 10 years of Malware for OSX article are actually trojans. Trojans require that a human being intentionally install the malware and give it permissions to run.
The Mac already comes with Apple's File Quarantine system, which has a trojan blacklist built-in that Apple maintains and updates. Since most trojans now are encrypted, I doubt a 3rd party app will do a better job than the OS.
To use a 3rd party anti-malware program, you have to give that program itself the run of your system and that causes it's own problems and opens its own potential security holes. The tradeoff just isn't worth it in the vast majority of cases.
So the question is, "Will 3rd party antivirus/antimalware programs compromise OSX's built-in security? "
If yes, in what way could it compromise the Mac?