Thousands of protesters have gathered outside the headquarters of Hungary’s public media corporation to demonstrate against what they say is a propaganda network operated by the nationalist government at the taxpayer’s expense. The protest was organised by Hungary’s most prominent opposition figure, Péter Magyar. He heads the TISZA party, which has emerged in recent months as the most serious political challenge for Prime Minister Viktor Orbán since he took power nearly 15 years ago. Magyar, whose party received nearly 30% of the vote in European Union elections this summer and is polling with…