Question

why did metternich describe as the most dangerous enemy of social order?

Answer 1

Metternich was the one who proposed the Treaty of Vienna. His ideology was conservetism. But Mazzini was young and vigorous. In order to pursue his vision he created many revolutionary society like Carbonari Young Italy and young Europe.
Thus this created conflict among them and metternich quoated the above words.

Answer 2

This is the apt answer for brief answer refer the guide