Someone with a vested financial interest in convincing you that your children will be be eaten by wild dogs if you don't give him money tells you that your children will be eaten by wild dogs if you don't give him money. Go figure.
As he notes, iOS is pretty locked down, and opportunities are almost entirely only in the app store. What he doesn't mention is that the app store is also pretty well locked down. Apple has done a fair job so far of reviewing software for nasty habits before allowing something in the app store, and a better than fair job of pulling stuff out when something nasty slips through. And, here's the important part, if something slips through, they can delete it remotely, which is to say, they have a pretty good anti-virus mechanism in place already.
Giving up enough information for outsiders to even try to build anti-virus apps for iOS simply spreads technical detail farther and wider, and honestly, increases the chance someone will find a vulnerability in the os itself.
And let's not forget, Kapersky has had their own web site hacked to distibute malware (the same sort of drive-by infection that an iPhone or iPad would most likely be vulnerable to, if someone could get at the internal details).
There are those who believe that anti-virus software itself is, basically, a form of grifting. I don't really agree with them (certainly not those who believe that most viruses are made and distributed by anti-virus companies), but I do see their point.
If I used Apple products, I'd prefer knowing that Apple kept those os details internal to having other companies making anti-virus apps, especially considering that most anti-virus software is so bloated as to render the system nearly unusuable. Not to mention screwups in updates. One managed to flag all emails with the letter "p" in them as malware, and Avast (I think it was) recently flagged one of its own definition updates as malware.