Now now....
The correct answer is "it depends".
Sure, if you're using Linux as a workstation then by all means forget the anti-virus.
But if you're using the Linux box as a server (e.g. file server, email server, whatever) that will be providing services to Windows machines, then you do need anti-virus ... as a filtering mechanism.
There is of course, an exception to the first paragraph about workstation use... and that is the wonders of rootkits. But you'll need something more specific than an AV program to scan for those.
Finally, none of the above means Linux has some magic invulnerability cloak. It does not. There are many ways to exploit a Linux machine, but none of them use what would traditionally be recognised as a virus.