There's no "right" to free speech in Hungary.
You might want to go and check Hungary's recently enacted Constitution before making those kind of remarks. Here, allow me.
Articles VII, VIII, IX, and X of the Fundamental Law of Hungary establishes the rights of freedom of expression, speech, press, thought, conscience, religion, artistic creation, scientific research, and assembly. Some of these rights are limited by the penal code.
Furthermore, none of the views expressed in the NPI conference fell under this:
Section 269 - Incitement against a community
A person who incites to hatred before the general public against
a) the Hungarian nation,
b) any national, ethnic, racial group or certain groups of the population,
shall be punishable for a felony offense with imprisonment up to three years.
Those detained by the Hungarian authorities were arrested because they weren't in possession of their passports. As alien as that may seem to you, you still have to provide your 'papers' in the supposedly democratic nation of Hungary if the police demand them. The only country within the European Union where this is not law is the United Kingdom.