They view Christians as radicals and traitors to their God because during the thirty years war Christians separated from the catholic church because the church at that time was tyrannical and corrupt and held errant beliefs. They are probably still upset because protestant groups ended catholic dominance of Europe. Christians, to the catholic mind, turned away from God and the way to heaven so they don't like us very much. Ironically catholics themselves are considered radicals and extremists by the eastern orthodoxy church because of the Great Schism.
In my 67 years as a Catholic, I have never heard a priest, bishop or even the pope denounce another Christian or non-Christian religion. They have no reason to. However, I have attended services (funerals, for example) and watched Protestant services on TV. It seems, at times, that these pastors would have nothing to preach about if it were not for their rantings against the Catholic Church.
The Catholic Church was established by Our Blessed Lord to save all people, it has been attempting to do that for 2,000 years now. 500 years ago, a few men who could not deal with their personal sins made up their own Church to allow them to live life the way they wanted. In doing so, they led many out of the Church that Our Blessed Lord, Jesus Christ, founded and guaranteed. Catholics do not "denounce" other Christians, they pray for them and attempt to bring them back into Christ's Church, which, through no fault of their own, was lost by their ancestors. Please do not listen to propaganda that has been handed down for generations, find out for yourself, go to a Catholic Church and ask to speak to the RCIA leader or the priest and find out for yourself what Our Blessed Lord teaches.