It seems you are comparing the ClamAV blog to the Intego website that is indeed trying to sell you something. This seems like comparing a magazine article to a magazine ad and complaining because the ad is, well, an ad.
If you compare the ClamAV with the Intego blog http://blog.intego.com (or any other commercial AV company blog for that matter) there is maybe a better comparison.
Apples to apples and all that...
Whatever Intego's behavior might have been in the past, they seem pretty honest these days. Ironically, just today there's a story on the MacWorld site crying wolf about a "trojan" called Tsunami, based on a Sophos report that also calls it a trojan. But it's not a trojan, it's just a hacker tool that would have to be manually installed to do any harm, and Intego is the only company so far (from what I've read) that points that out clearly, adding that any risk is very low. Seems like pretty honest behavior, considering they could have talked it up like everyone else and used that to sell their software.
Of course, that does not say anything about the merits of their software. I've seen people with frequent kernel panics where the panic reports implicated VirusBarrier, and removing VB was an instant cure. So, while it may work fine for many, there are potential dangers involved with using it.