Yes, Pope Pius XII was right to use Vatican resources to fight the forces of the Left in Italy and Europe in general, because he was standing up for the minority that was being oppressed. As Pope, it was his job to take a stand and do the right thing, respecting the dignity of all human life. His actions were commendable.
No, it was wrong to use the resources of the Vatican to engage in conflict at all. The purpose of the Church is to bring God's peace and salvation to the world. Using church resources to engage in any sort of hostilities goes against that mission and should not be accepted.
While, I have heard Pope Pius XII was a key player in defending the Jewish people from the Nazis. He seemed to let this issue go to his head. This is why religion needs to stay out of politics. I do not know why people have to persecute other people who do not have the same viewpoints as you? As long as they are not hurting anyone with those viewpoints. In my opinion he was wrong on this issue.
Though obviously people are entitled to their political opinions, and its naive to assume that reigious leaders and officials have no leanings in politics, a religious organization should not take official stances politically. Organizations should probably take stances when they are relevant, but not to the point of taking sides with politicians.
I think that a Pope who uses resources from the Vatican to fight groups that he may disagree with, it is a serious breach of trust among his followers and people of the faith. I think that using such power is not something a servant of God should be doing.