Not sure how it is in Hungary, but in Poland ISP subscriptions are taxed by VAT, I think its 23%. Actually, almost everything is taxed like that. So why tax it again? If ISP would charge me per gigabyte then that would be taxed by VAT as well. They don't charge me like that (unless its mobile network), so there should be no tax on this either.
Yes, there is stuff that is taxed not just by VAT, for example alcohols, tobacco, petrol and such. Is that fair? Debatable, since you could argue "They cost public money due to health issues and roads are maintained by public funds as well". Network infrastructure? Is it owned by Govt, or corporations? if Govt, then sure - they should charge for usage or by some other kind of scheme, but if its privately owned, then I think Govt should fuck off.