Mussolini started out as a socialist, then opted for his own rise to power. The black shirts brutalized the socialist and communist opposition. Sending them into exile, murdering or imprisoning them. Let's not forget the Rosselli brothers. There is far more to socialism than the few, very few, economic policies Mussolini retained from his early days. Il Duce destroyed labor unions and was the darling of industrialists worldwide;in the 1920s the Wall Street Journal published odes in his honor on their front page! Hardly the work of a socialist. And of course Begin wanted the Irgun in the Jewish Brigade! As you say yourself, what better way to get arms and training?
Bomb in Lebanon targets bus heading to Syria, no casualties (Reuters)
from the article: Book links Begin to 1952 plot to kill then-German Chancellor Adenauer