He urged them to fight "with determination ... the risk of political and legislative decisions that contradict fundamental values and ethical principles rooted in human nature"
The Pope said they had to defend "the family based on matrimony, opposing the introduction of laws on other forms of unions which would only destabilise it and obscure its special character and its social role, which has no substitute".
In another section of his speech, the Pope stated that the Church had to say "'no' to weak and deviant forms of love".
He said the Church wanted instead to say "'yes' to authentic love, to the reality of man as he was created by God".
In his address to the Catholic convention, the Pope was also applauded when he said the Church had to continue to defend "life in all its phases, from conception until natural death".
He said the Church did not want to be "a political agent" but wanted to help shape social policy.