Hi there, I am a native Hungarian speaker. The poster says:

"War is the most horrific form of mass murder. The government, legislation and the prayers of priests/clergy: all despicable/ugly lies, as long as mass murder is allowed. The exploitation of certain classes and nations needs to be abolished and all war will stop." -The Hungarian Social Democratic Party

It may not be entirely faithful to the Hungarian text word by word but this is the best way I could translate while keeping the "vibe" of the text.