Antivirus is NOT important unless you're old or a moron. Not run an antivirus full time since the 90's and never found a virus on the occasion I did install it and checked. Don't run dodgy executables, don't open any email attachments that came from an unknown sender, ignore popups on websites, don't install any programs unless it was developed by a reputable company. Follow those rules and use a bit of intelligence, and you'll never have any issues. However, your average person is a fucking moron therefore the proliferation of antivirus software.
Not true, only way you'd be safe is to disable scripts/flash/java or even the most cautious would still get virus/malware, 10 years ago your school of thought worked, now not so much