The possible Democratic candidate made his remarks in an interview with The Des Moines Register. See video.
The former governor of Maryland conveniently overlooks the Catholic church’s teaching on this particular issue:
If it is true that all Catholics are obliged to oppose the legal recognition of homosexual unions, Catholic politicians are obliged to do so in a particular way, in keeping with their responsibility as politicians. Faced with legislative proposals in favour of homosexual unions, Catholic politicians are to take account of the following ethical indications.
When legislation in favour of the recognition of homosexual unions is proposed for the first time in a legislative assembly, the Catholic law-maker has a moral duty to express his opposition clearly and publicly and to vote against it. To vote in favour of a law so harmful to the common good is gravely immoral.
When legislation in favour of the recognition of homosexual unions is already in force, the Catholic politician must oppose it in the ways that are possible for him and make his opposition known; it is his duty to witness to the truth. If it is not possible to repeal such a law completely, the Catholic politician, recalling the indications contained in the Encyclical Letter Evangelium vitae, “could licitly support proposals aimed at limiting the harm done by such a law and at lessening its negative consequences at the level of general opinion and public morality”, on condition that his “absolute personal opposition” to such laws was clear and well known and that the danger of scandal was avoided.(18) This does not mean that a more restrictive law in this area could be considered just or even acceptable; rather, it is a question of the legitimate and dutiful attempt to obtain at least the partial repeal of an unjust law when its total abrogation is not possible at the moment.
The Church teaches that respect for homosexual persons cannot lead in any way to approval of homosexual behaviour or to legal recognition of homosexual unions. The common good requires that laws recognize, promote and protect marriage as the basis of the family, the primary unit of society. Legal recognition of homosexual unions or placing them on the same level as marriage would mean not only the approval of deviant behaviour, with the consequence of making it a model in present-day society, but would also obscure basic values which belong to the common inheritance of humanity. The Church cannot fail to defend these values, for the good of men and women and for the good of society itself.