A tax is a way to collect money, it can be set in boundaries so as to not be unilaterally applied without limits.
Being not completely uneducated, I think that they may have thought about the "every heavy internet connected business will go broke and youtube/steam will go down" if they simply ask a no-limit fixed sum of money for each transfered gigabytes, technical issues aside.
In the link the OP provided they precisely talk about a 700 forints (2.26€) monthly cap. I dont know whats 2.26€ for an Hungarian, but to me it doesnt look much of a tax raise except for the poorest of the poor. Whatever the sum asked, its something less for the people to spend on what they want, for that reason its normal that people are not happy about this, new tax never made anyone happy, except the state.
I read anti-democratic and authoritarian measure... What? A government which proposes a law about a tax, and put it to vote, is completely normal procedure. If you dont like it, you protest against it, and you dont vote for the people who proposed and wanted the law, even try a coup.
I'm old enough to have lived with limited access costy internet, and my country was not a tyranny. Today most advanced countries have "unlimited" bandwith internet package offers, but nothing says that it will stay that way forever, for technical reasons and for business plans reasons. Nothing is granted.
When you win elections in a democracy, you get to a position where you can propose stuff. Today Hungary actual dominant political party propose that a tax should be applied to internet. As a fellow heavy traffic internet user, I feel empathy for the Hungarians if it is applied by politicians that does not know exactly how internet and data transfer works and if it has a heavy impact on everyone concerned.
In the case it doesnt, and those in charge of the development of that law have one brain together, we can safely assume that this will be just one tax...
It concern a symbolic place of freedom, internet, and can be seen as backward innovation in comparison with the actual domination of unlimited internet access, but I do not think it has to become an ideological debate except if we reallllllyyyyyyy want it to become so, with the help of bad semantic, hype media and the old-new cold war trend of today.