I agree, this position lacks any logic. Traditional Catholicism teaches that sex outside of a sacramental marriage is always sinful regardless of the gender of the participants or the legality of marriage in their particular country. For the leader of the church to take such a relativistic view does nothing but further confuse the issue.
Did the proposed Italian civil union legislation specify that that the civil participants would be “spouses” or that the union would be predicated upon sexual intimacy?
If not, it might have been legislation -— without reference to sodomy -— that could benefit anybody, e.g. family members who share a household and finances, and are permanent caregivers for a disabled son, sister, grandmother.