The 39-year-old son of former Liberal Prime Minister Pierre Trudeau said he was raised Catholic by his father, going to church every weekend and saying prayers nightly as a family.
The elder Trudeau's Catholicism has been well documented in biographies, including one book specifically on his faith. The former prime minister was educated by the Jesuits and admitted to going regularly to church up until the last years of his life.
"I have to say, I'm really surprisingly upset. I didn't think I would be, but I am," Trudeau told The Canadian Press on Tuesday evening.
"For someone to start questioning my own faith and accusing me of being a bad Catholic, is something that I really take issue with. My own personal faith is an extremely important part of who I am and the values that I try to lead with."
Trudeau added that neither he nor his father saw any incongruity between enshrining the rights of gays and lesbians, for example, and the tenets of Catholicism. He notes that he is personally very opposed to abortion, but still believes nobody can tell a woman what she should do with her body.
"My own credo is completely consistent with that, and I'll defend my own faith and my own values to the utmost extent," Trudeau said.