This only really goes to the "don't entirely trust their statements regarding their product being the only effective barrier" part of the story. Reputable anti-virus companies do have a huge conflict of interest reporting on viruses they find and can tackle, but they also remain an important source of information about viruses. Disreputable anti-virus companies sell product which could be as simple as a "hollywood OS" green stripe animated GIF which says "virus cleaned" for all they really do: they probably install more malware rather than removing any.

Also, an anti virus company saying they can't understand how a virus remains infected after removal is interesting.