It's not a question of a hacker finding a way in, it's a question of wether it's worth his while. It is probably easier to hack Windows and its certainly more worthwhile for a hacker to spend his energy hacking Windows computers as they are still most numerous operating system out there. That the main reason Macs are generally not at risk is that 99% of the viruses etc out there are targeted at Windows.
In my opinion it's still quite safe to operate a Mac without any additional antivirus tools. However be aware that although a Mac may not be affected or vulnerable to a virus it receives (say via email), that virus could easily be passed along to, and infect a Windows machine by forwarding the email to a Windows user.
In general I believe that a Mac is a much more reliable & easier to maintain home computer system. This is mostly because of the reduced vulnerability to viruses and other malicious applications but also because Apple control both the hardware and operating system, making for a more tightly quality controlled and integrated system. Also if you stick to third party applications (both free and paid ) via the Apple App store a similar degree of control is applied to the 3rd party applications, potentially promising better reliability & quality.
I say that as an IT professional with over 20 years managing Windows based commercial systems but have used Macs in my home environment for the last 10 or more years. In that time I have not used any full time antivirus software, but have checked my Macs every now and again - but have never found a virus that infected them but have found emails to have contained Windows viruses/malware. In contrast I have found unprotected Windows machines to have been virus/malware infected within seconds of connecting to the internet.