The author states that foreign students _plan_ on staying in Germany, however that is not what is actually happening. 41% of students abandon their studies before they have a degree. Out of the students that finish their degree, only 36% remain in Germany. Out of those remaining, more than half of them need more than 1 year(!) to land a job, indicating that they may not have the best grades or skills.
Furthermore, many seem to assume that Germany somehow needs to offer this tax payer subsidized "free" university program to attract foreign students to fill shortages in the workforce. This is not the case. First, despite constant media reports saying otherwise, there is no major talent shortage expect in very few niches. Second, any EU-citizen (thats 600+ million people outside of Germany) can work in Germany without any permission required. Third, for non-EU citizens there already is a visa program (the "blue card") that allows them to work in the EU if they are qualified, e.g. have a Masters degree from their home country.
In summary: German tax payers are asked to fund the education of foreigners at little to no return. Given the "free" nature of the program, it attracts rather unqualified students (or, lets say at least not the top notch).
All this may sound harsh but it is simply not the job of German tax payers to provide some sort of indirect third-world aid to middle/upper-class students from foreign countries.