Well said Ian. I completely agree with everything you say.
I think the level of support offered by WebAssist is fantastic. They are here to provide support with their software extensions, not to provide support for every other hardware/software/security related question (even though they often do).
If you're offering a professional service to a client it's up to you to research things outside of the normal scope to ensure that you fully understand and are aware of the implications of putting something into place.
Security Assist is an extension to keep web pages hidden from non-authorised users, it is not a product to provide web server security.
On the other side of the coin I can appreciate that finding out your website has been hacked is not a nice feeling, but maybe you should talk to your hosting company or investigate whether anyone has shared their log-in details with another person in order to get to the bottom of the problem.