'When the people read it, they were delighted with the exhortation.'

"It is the decision of the Holy Spirit and of us not to place on you any burden beyond these necessities, namely, to abstain from meat sacrificed to idols, from blood, from meats of strangled animals, and from unlawful marriage."

People have been complaining lately about the lectionary, whose fabricators seem, calculatedly, to have omitted "hard sayings."

Well, what about the Canon of the Bible itself having omitted the next couple verses in Acts, huh? What about that?

But that "abstain from unlawful marriage" thingy? Don't worry, Silas and Judas will look to the reality of the family today in all its complexity.
Some of our members, (those judgy ones who went out to you without any mandate,) find it hard to make room for the consciences of the faithful, who are capable of carrying out their own discernment in complex situations. We are called to form consciences, not to replace them.
Marital problems often give rise to new relationships, new couples, new civil unions, and new marriages, creating family situations which are complex and problematic for the Christian life Therefore, while clearly stating the Church’s teaching, the prebyters are to avoid judgements that do not take into account the complexity of various situations. Some of the brethern lack the training needed to deal with the complex problems currently facing families, and issues involving  marriages with pagans require particular attention which contain numerous elements that could well be made good use of and developed, both for their intrinsic alue and for the contribution that they can make to the ecumenical movement.
For those in unlawful marraiges, consider - because of forms of conditioning and mitigating factors, it is possible that in an objective situation of sin – which may not be subjectively culpable, or fully such – such persons can be living in God’s grace, can love and can also grow in the life of grace and charity, while receiving the Church’s help to this end. In certain cases, this can include the help of the sacraments. 

Someone leave out those words to the Antiocheans, (Antiochites? Antiochers?) deliberately?
Maybe St Luke decided Olden Days People didn't need them.
Our problems, of course, are very different from Olden Days People.
Because... complexity.