You don't relly need anti-virus for Linux, especially if you put your built-in firewall up when you are on public wifi (at Starbucks, for instance). For Linux to get infected, an attacker needs physical access to the machine, or for you to do something that lets him in.
But if you install clam-av, that will catch Windows viruses that fly past, and stop them, so you don't pass them on to infect your friends and family. Call it being a good neighbour.
clam-av does not really need a user interface, but if you want one, install clamtk.
Myth-busting: "the entire Linux platform is not even a 10th as popular as Windows"
(1) "popular" means that people like it - not true of Windows
(2) 80% of servers on the web are running Linux. Linux is 95% of all new servers - the Windows servers are mostly ageing, that the owner will not upgrade.
(3) 1.5 billion smartphones running Linux. Windows smartphones not even 1% of all smartphones.