Actually, Paul banned all motivations and desires which would culminate in the commission of sinful acts, while stating clearly that in order for us to perform righteous acts, the motivations for those acts had to be righteous in-and-of themselves:
So I say, live by the Spirit, and you will not gratify the desires of the sinful nature. For the sinful nature desires what is contrary to the Spirit, and the Spirit what is contrary to the sinful nature. They are in conflict with each other, so that you do not do what you want. But if you are led by the Spirit, you are not under law.
The acts of the sinful nature are obvious: sexual immorality, impurity and debauchery; idolatry and witchcraft; hatred, discord, jealousy, fits of rage, selfish ambition, dissensions, factions and envy; drunkenness, orgies, and the like. I warn you, as I did before, that those who live like this will not inherit the kingdom of God.
But the fruit of the Spirit is love, joy, peace, patience, kindness, goodness, faithfulness, gentleness and self-control. Against such things there is no law. Those who belong to Christ Jesus have crucified the sinful nature with its passions and desires. Since we live by the Spirit, let us keep in step with the Spirit. Let us not become conceited, provoking and envying each other. (Galatians 5:16-26,NIV)
Under the heading 'the acts of the sinful nature' we find every desire and motivation which has culminated in the commission of a sinful act. And under the heading 'the fruit of the Spirit' we find the motivations which are necessary if we are to truly perform acts of righteousness. The old saying, "He did all the right things, but for all the wrong reasons," needs to be taken to heart by those of us who are Christians. You cannot pick good fruit from a tree whose roots are planted in poisoned soil, and you cannot perform righteous acts while using the motivations which are clearly part of the sinful nature. In order for the acts to be righteous, the impetus for those actions must also be righteous, and that can only occur when that impetus is the motivations listed as the fruit of the Spirit.
There were those who opposed Paul because he stood against compulsory circumcision for all Gentile males who converted to Christianity, as well as not requiring Gentiles to adopt purely Judaic societal laws. But they never accused Paul of being immoral, or of condoning immorality. His epistles are quite clear in their telling the new Gentile converts that there were actions which, even if they had participated in their commission before they converted to Christianity, they were now to see as offlimits to them.
But he not only told them what they could and could not do as Christians, but also told them how to accomplish this. Obeying a set of laws wouldn't work. As the heart went, the body followed, and if the heart was led by the sinful nature, all the laws in the world wouldn't do any good. So he realized that the sinful nature would have to be 'reined in', and that would take the direct intervention of the Spirit, and then the motivations which are recognized even today as the source of all that is good needed to be implanted in the converts, and that would also take the direct intervention of the Spirit.
So Paul was not against morality; far from it. He simply knew that there was a way in which that morality could become an integral part of the new convert's life and everyday experience. And that way was through their putting their trust in God, and by so doing opening their hearts up to his ability to 'reprogram' their desires and motivations so that those desires and motivations could conform to what God wanted of them.