He was not just anti-catholic, he was flat out anti-religion, as well as anti-government, as well as anti-war. However most of these stances came later in his life after many accumulated personal tragedies.
Among them, his younger brother was killed in a riverboat explosion, his son died in childhood, his youngest daughter died of menengitus, his wife lingered and died of heart failure, in the last decade of his life his eldest daughter decorated his house for christmas, went upstairs to take a bath, had a seizure, and drowned in the tub. The last two decades of his life his writing to took a very dark turn and he really succumbed to cynicism.
Of course he was always a very liberal man, for his time. He had a life long distaste for any persons or organizations he saw as controlling people’s lives, which is a very american way of thinking by the way.
He was a man of contradiction though. Twain hated the wealthy for their greed and opulence, but also desired more than anything to become rich and influential. He ranted against religion, but wrote a very good book on the life of St. Joan Of Arc (a book which he considered his favorite and best work).
Read some of his books, what you’ve heard about him is not as important as what those stories say about the human condition, about our spirit.
Sorry if this was a little ranty or incoherant its midnight here and I’m tired.