I'm not sure why this tax should be labelled as absurd. Lots of countries tax TV, phone already. Taxing social media sounds weird only because no one else has done it yet.
Taxing social media is like taxing you for saying or hearing a specific word or sentence on the phone, or every time a certain show is broadcast on the TV.
This is absurd, and a violation of free speech, as it discriminates content. It is an attempt to control information exchange by discouraging it. The ulterior motive is usually manipulation of the citizens to keep them in line in absurd regimes, and/or to avoid the outside becoming aware of their internal issues.
Separately, these idiocies implemented by people that do not understand how the internet works undermines fundamental security aspects by being incompatible with proper cryptographic security measures. You cannot, for example, serve a portal instead of a properly configured HTTPS site without your browser noticing, so HTTPS needs to be blocked first.