Are customers really that dumb?

I am quite often designing new marketing collateral for several products and services.  The most recent is a 2-sided 8.5x11 page that is included with the "welcome kit" explaining what a brand new customer can expect from the service they have just signed up for. Just before going to press, the president of that company called me and asked that we put one small sentence on the bottom of each side.  Our chat conversation went much like this:

Him:    just add "See reverse side for more information."
Me:    do you really think it needs it?
Him:    yes. people are dumb.

So the question is this: Are consumers really that dumb?

I'll admit, sometimes consumers need to be helped along.  Surf the web for just a few minutes and you'll see "click here," "next," "go to," "sign up here" and similar messages plastered all over your screen.  On outdoor advertising, "Exit now," "Next exit," or "X miles ahead" are also common.  But let's put that in context.  The average time available for a driver to read an outdoor sign is 7 seconds.  On the web, it's estimated that the average time a visitor spends per page is just over 20 seconds.

What does that mean? You've got to get the customer's attention! Tell them what to do, where to go, and when to do it!  And you need to do it in no uncertain terms because if you don't, their going to miss it.

In contrast, this printed piece was being delivered to someone who has already invested time and money into this service. 

IMO: No, customers are not that dumb.

What do you think?