It is true that you have not said so, but you did imply it. It is true that rationalism did not produce fundamentalism, but it is equally true that fundamentalism is not caused by rationalism.
If you agree with the first half of the proposition, than logically and epistemiologically we must agree with the second inference drawn out of the first premise.
Thus it becomes easy to conclude, that fundamentalism is not the byproduct of rationalism. It will become a tautology to link the ism's and conclude without refuting the correctness of the premises.
Now, i agree with you and your source, that fundamentalism is, among others, a byproduct of modernity. The source/author has misled you, however, into thinking, that if i mix up 'rationalism' with 'modernity', than one can safely conclude that the product called fundamentalism being a byproduct of 'modernity', and modernity, since it largely, stems from rationalism, hence fundamentalism is also the byproduct of rationalism is not just a bit but quite enough misleading.
My representation was only to point this out. If you think the above is wrong, than i am sorry to be wrong.
okay just an after thought. The above was just to clarify my stand against what your claim or observation was. I do understand what you mean, i.e the general idea that rationalsim and modernity has contributed as factors to fundamentalism. The extent of which can be disputed, thats all. I do not want to hijack or divert your point on a minor scuffle for semantics or appropriate wordings.
So, i broadly agree with you.