Sexual immorality is what bothers Christian leaders more than anything else. As far back as the Book of Acts and the problems between Jewish Christians and their newer Gentile Christian brothers, immorality of the sexual variety, was what tended to set them apart.
It's odd to imagine that those early gentile Christians and their obsessive interest in sexual immorality, were, nevertheless, Christians. They obviously wanted to be Christians in good standing, otherwise why the big fuss about the problematic differences regarding meat sacrificed to idols, the eating of blood (in blood pies, or blood sausages, or other blood-based foods that were popular at the time), and eating the meat of strangled animals.
Some modern liberal Christians I've met through the years were very much Christians in that they showed an unnatural zeal for things Christians. Simultaneously though, they also demonstrated an interest in either sex outside of marriage with one partner, or in other cases, sex outside of marriage with someone of their own sex. Both are condemned by conservative interpreters of the Bible. These modern liberal-leaning Christians are in good company, nevertheless, with some of the gentile Christians described in the book of Acts who along with the meat and blood food stuffs already mentioned, also had a preference for sexual immorality.
Today, very few Christians bother with meat sacrificed to idols, meat of strangled animals or blood-based foods. If some do happen to eat any of these, however, it doesn't offend anyone except perhaps animal rights activists, and devout vegetarians. The free-sex penchant is still very much frowned upon, however.
One important point I need to make is that these stripped-down guidelines that were put forward to keep the peace between Jewish Christians and gentile Christians make avoiding sexual immorality, and the dietary prohibitions, more important--at least in this situation--than the more important considerations of practical Christianity and sharing your bread--or meat--with your hungry brother. But perhaps that was best left for another chapter in early Christianity. See the epistle of James or the parables of Christ for references to doing unto others as you would have them do unto you, and not just wishing them a nice day while they were deprived of bread, clothing or shelter.
It boggles the mind--to overstate the case--that some gentile Christians who may or may not have possessed all of the fruit of the Spirit, e.g., love, hope, faith, etc., but not self-control, obviously, were also wont to engage in activities that Jewish Christians found to be sexually immoral. What might some of these have been? Sex with prostitutes? Yes, especially since Paul counsels Christians against uniting their bodies with that of a prostitute in counsels to Christian churches of the time. Sex with family relations? Yes, there was the infamous case of a church member who apparently was in good standing--until Paul censured him--who was having sex with his wife's mother. Sex with temple prostitutes? Again, yes, especially by newly converted Christians. I'm referring to Paul's statement containing the words, "and such were some of you."
What am I getting at here anyway? That some--or perhaps many--early gentile Christians had a more relaxed attitude toward sex outside of marriage than Jewish Christians? That sounds very contemporary to these ears. Yes, sex outside of marriage has its problems: disease, hurt feelings, rejection when the attraction fades, unwanted pregnancies, angry spouses of the unfaithful partner. The list can go on and on.
I mention these somewhat tawdry references because texts like those in Acts 15:19-21, 28-29 are sometimes glossed over and ignored or, if they are not, then only the sexual immorality reference is played up, while the meat and blood prohibitions are ignored. Yet the latter prohibitions were obvisously very seriously considered at the time, so much so, that the counsel of the Holy Spirit is mentioned in stipulating that blood-based foods be avoided.
Nevertheless, when all is said and done what else can I say, in closing, but to quote the concluding words of these excerpts: "you will do well to avoid these things. Farewell."