Overestimated human rationality.
The benefit of such a platform is questionable because human interaction is mainly governed by emotions. They often have more effect on decisions than rational arguments.
Emoitions are not the only decesive aspects.
The original theses does not claim that emotions do not play any roll. But rational arguments also play a role. Especially for the mentioned target group. If there is a possibility to state rational arguments more clearly and to iteratively improve them, then this is likely to increase the quality of discussions.