I am not sure what you find so funny.
First off I am going to concede without argument we use the no. 40% not 80%. which I used representing engage university level critical thinking to be able to think abstractly and challenge the Koran without simply feeding it back without question. I will agree that 80% is unfair and simply use the 40% illteracy number most sources today will quote including:
:
https://ummid.com/news/2015/February/11.02.2015/literacy-in-muslim-world.html
which states:
" Illiteracy is stunningly rampant in the Muslim world. Nearly 40 percent - with varying percentages in the member states of the Organization of Islamic Cooperation (OIC), of the Muslim world's population cannot read or write.
It means that there are hundreds of millions of illiterates in the OIC countries, mostly female, according to a report prepared by the OIC.
The report, a copy of which is obtained by the International Islamic News Agency (IINA), showed that adult literacy rate in the OIC countries is roughly 73 percent, lower than the global adult literacy rate (82 percent), and the rate of other developing countries (85 percent), based on 2013 statistics.
...
The illiteracy rate in the Muslim world ranges between 40 percent among males and 65 percent among females, with rural areas lagging behind urban areas by over 10 percent, said the Islamic Educational, Scientific and Cultural Organization (ISESCO).
Literacy indicators are still not encouraging, given the fact that there are still 57 million children (many of them in the Muslim world) out of school worldwide, a matter which will constitute a growing burden of illiteracy rates in the long run."
Also I refer to:
https://files.eric.ed.gov/fulltext/EJ1159514.pd which stated:
"Illiteracy in the Arab world is becoming an urgent necessity particularly facing problems of poverty, ignorance, extremism, which impede the required economic, social, political and cultural development processes. Extremism, violence and terrorism, in the Arab world, can only be eliminated by spreading of knowledge, fighting illiteracy. The study shows that illiteracy rate among males in the Arab world is 25% for males, (46%) for Females. Results of the study show that if the educational situation in all Arab countries does not change, illiteracy rates will increase in the Arab world, and the number of illiterates in the Arab world will reach 49 million in the category of age of 15 years, and by 2024,it may reach 5.5 million of youth (15-24 years). The study identifies factors affecting the rise of illiteracy in the Arab world, particularly: "Low economic level of many Arab countries, the growing security, political turmoil and internal problems experienced by most Arab countries, Social reasons, and random policies and contradiction in the trends and areas of combating illiteracy." The study concluded that illiteracy has a significant impact on social behavior, and that democracy, political participation, violence, cultural development, respect, pluralism, and accepting diversity, are all affected by illiteracy. The study recommends that Arab governments must formulate clear strategies linked to development plans to save 100 million Arab citizens who suffer from illiteracy, and ignorance. Illiteracy is to be taken seriously because it entails misunderstanding democracy, lack of youth interest in political affairs, corruption, and therefore the absence of comprehensive reform programs."
The percentage no. is not the issue and illteracy in the Muslim world is not a laughing matter.