Maybe no need for a anti-virus now, but I can see it being needed in the future as Macs continue to grow in popularity.
Not necessarily bad logic.

Except folks have been saying this since 2001…when OS X was first released. EVENTUALLY…if "they" keep saying this…EVENTUALLY…"they" will be correct!
This is just like the unhappy mother-in-law saying on the day of the wedding…
"This marriage will never last!" If she keeps saying this long enough…she may eventually be right.
Then 40 years later (when the couple is now 60 years old…and she's 85)…the couple unfortunately gets divorced. Then the 85 year old mother-in-law says…
"See I told you the marriage would never last!"
If someone keeps saying something long enough…there's a good chance eventually it will come true. So far we (Mac Users) have had 13 years free of these sort of headaches.
Using this logic…does that mean we should have suffered (needlessly) with the downsides of installed anti-virus software for the past 13 years??
- Nick