"Those who attack the Church of Christ by teaching that Christ's Church is divided into so-called 'branches' which differ in doctrine and way of life, or that the Church does not exist visibly, but will be formed in the future when all 'branches' or sects or denominations and even religions will be united into one body; who do not distinguish the priesthood and mysteries of the Church from those of the heretics, but say that the baptism and eucharist of the heretics is effectual for salvation; therefore, to those who knowingly have communion with these aforementioned heretics or who advocate, disseminate, or defend their new heresy of Ecumenism under the pretext of brotherly love or the supposed unification of separated Christians, Anathema!"
If one reads the anathema carefully, one will see that the words 'aforementioned heretics' do not mean the objects of the Anathema. i e. the ecumenists. These words refer to the heretics mentioned in the first phrases of the anathema. i.e. the heretics previously identified by the Church, such as Roman Catholics, Protestants, etc. The Anathema therefore denounces those who would have communion with Roman Catholics, for example.