I think that it's self-evident why a court ruling that forced conversions are not valid carries more weight than a textbook for grade schoolers. But the issue is worth addressing because the chidlren's textbooks used in Egypt are actually a sign of increasing tolerance, not less.
In my elementary school in suburban Chicago, I was taught Manifest Destiny of the United States and that the Native Americans were savage but noble people who are now protected citizens and have embraced modernity. I think that there are few people in my generation who still subscribe to this view, despite having been "indoctrinated" as impressionable youth. And certainly my grade school textbooks have no relevance to many court rulings in favor of the Indian Nations that say that the treaties they signed with the US were continually and habitually broken.
But let's look a little more closely at the textbooks in question. The translation seems pretty poor to me, but here's the whole paragraph:
If a Protected Person [Dhimmi] is forced to convert to Islam, his conversion is valid. If a Harbi [non-Muslim alien] is fought against and converts to Islam - it is valid... If the [same] Dhimmi returns [to his former religion], he is not killed [like an ordinary apostate], but imprisoned until he converts to Islam [again], because there is doubt regarding his belief [when he was forced to convert]. There is a possibility that it [i.e., his forced conversion] was sincere, so he is to be killed as an apostate. It is [also] possible that he did not believe [in Islam while having been forced to convert] and then he [should] be a Dhimmi and shall not be killed...
The reason I say the translation is poor is because the first sentence is an absolute one, that is directly contradicted by later ones. In actuality the assertions were probably more nuanced - Arabic is not a language that lends itself to machine or brute force translation.
Also it is worth noting that textbooks are often a vehicle for social activists to push their social agendas. Their value in this is beyond dispute; look at the turf war over textbooks being fought in the Evolution/Intelligent Design debate. The specific textbook in question is one issued by Al Azhar university, which is not a monolithic entity but actually has numerous factions ranging from liberal modern to islamist medieval. The CMIP notes that textbooks issued by the Ministry of Education are much more reasonable, and that in general the textbooks used by school children are much more tolerant than they were in the past. If you read the entire report you get a much more nuanced picture. Also keep in mind that the passage above is from 2002.
Are children's textbooks in Egypt still intolerant by our standards? Well, if by "our standards" you mean the United States circa 2006, then yes, absolutely. If you mean 1956, then no. Given that the trends are pointing in the right direction I think that it's pretty disingenious to try and use these textbooks as evidence of how the precepts of Islam dictate that "any muslim" (Sensing's words, not mine) would consider a forced conversion valid.
The bottom line is that a textbook is just a textbook. It's not the Qur'an, which I quoted in my earlier post. And the fact that there are jurist rulings on how forced conversions are not valid pretty much overrules any textbook-derived analysis.