As for the one who is weak in faith, welcome him, but not to quarrel over opinions. Romans 14:1

kit: Miss Dottie and Mr. Brad at the Zoo by Kits 4 Kids

Below is the context of the entire chapter. The key word of the above verse is "opinions." Paul is not contradicting himself when he said in 1Cor. 5 to purge the leaven and remove the evil person who is committing sexual immorality from among them. The goal was restoration of the person to fellowship when they repented, rather than letting them be deceived into thinking that sort of behavior is acceptable for children of God. (2Cor. 2:5-11, 2Cor. 13:10-14) This passage cautions those who tend toward legalism to remember we are free of the letter of the law and will be judged by the law of liberty. (John 1:25, John 2:8, Rom. 7:6, 2Cor. 3:6) We are not to decide on His behalf whether or not each member of the body's contribution is valuable or acceptable. We will each be judged by Jesus. (Rom. 12, 1Cor. 12:1-13:13)

As for the one who is weak in faith, welcome him, but not to quarrel over opinions. One person believes he may eat anything, while the weak person eats only vegetables. Let not the one who eats despise the one who abstains, and let not the one who abstains pass judgment on the one who eats, for God has welcomed him. Who are you to pass judgment on the servant of another? It is before his own master that he stands or falls. And he will be upheld, for the Lord is able to make him stand. One person esteems one day as better than another, while another esteems all days alike. Each one should be fully convinced in his own mind. The one who observes the day, observes it in honor of the Lord. The one who eats, eats in honor of the Lord, since he gives thanks to God, while the one who abstains, abstains in honor of the Lord and gives thanks to God. For none of us lives to himself, and none of us dies to himself. For if we live, we live to the Lord, and if we die, we die to the Lord. So then, whether we live or whether we die, we are the Lord’s. For to this end Christ died and lived again, that he might be Lord both of the dead and of the living. Why do you pass judgment on your brother? Or you, why do you despise your brother? For we will all stand before the judgment seat of God; for it is written, “As I live, says the Lord, every knee shall bow to me, and every tongue shall confess to God.” So then each of us will give an account of himself to God. Therefore let us not pass judgment on one another any longer, but rather decide never to put a stumbling block or hindrance in the way of a brother. I know and am persuaded in the Lord Jesus that nothing is unclean in itself, but it is unclean for anyone who thinks it unclean. For if your brother is grieved by what you eat, you are no longer walking in love. By what you eat, do not destroy the one for whom Christ died. So do not let what you regard as good be spoken of as evil. For the kingdom of God is not a matter of eating and drinking but of righteousness and peace and joy in the Holy Spirit. Whoever thus serves Christ is acceptable to God and approved by men. So then let us pursue what makes for peace and for mutual upbuilding. Do not, for the sake of food, destroy the work of God. Everything is indeed clean, but it is wrong for anyone to make another stumble by what he eats. It is good not to eat meat or drink wine or do anything that causes your brother to stumble. The faith that you have, keep between yourself and God. Blessed is the one who has no reason to pass judgment on himself for what he approves. But whoever has doubts is condemned if he eats, because the eating is not from faith. For whatever does not proceed from faith is sin. We who are strong have an obligation to bear with the failings of the weak, and not to please ourselves. Let each of us please his neighbor for his good, to build him up. For Christ did not please himself, but as it is written, “The reproaches of those who reproached you fell on me.” For whatever was written in former days was written for our instruction, that through endurance and through the encouragement of the Scriptures we might have hope. May the God of endurance and encouragement grant you to live in such harmony with one another, in accord with Christ Jesus, that together you may with one voice glorify the God and Father of our Lord Jesus Christ. Therefore welcome one another as Christ has welcomed you, for the glory of God. Romans 14:1-15:7

If Paul were suggesting "to each his own" in regard to choice of whether to sin and in what way, then he would not have preceded it with this:

The night is far gone; the day is at hand. So then let us cast off the works of darkness and put on the armor of light. Let us walk properly as in the daytime, not in orgies and drunkenness, not in sexual immorality and sensuality, not in quarreling and jealousy. But put on the Lord Jesus Christ, and make no provision for the flesh, to gratify its desires. Romans 13:11-14

In a similar way, he preceded the discussion about the various functions of the members of the body of Christ in Rom. 12:3-8 with this (and he continued on in Rom. 12:9-21 with many specific examples of how to please God by our behavior):

I appeal to you therefore, brothers, by the mercies of God, to present your bodies as a living sacrifice, holy and acceptable to God, which is your spiritual worship. Do not be conformed to this world, but be transformed by the renewal of your mind, that by testing you may discern what is the will of God, what is good and acceptable and perfect. Romans 12:1-2

So once again, verses of Scripture should not be taken a la carte. It all goes together so that we can be equipped with the knowledge we need and to put it into PRACTICE. Then we can be assured of hearing "well done, good and faithful servant" when Jesus returns. (2Tim. 3:10-17, Titus 2:11-15, Col. 1:10, 2Pet. 1:3-15, 2Pet. 3:11-18, Matt. 25:21) As Paul says below, we are meant to encourage one another to do so, not to pick at each other and tear one another down. (Heb. 10:23-30, Gal. 6:7-10)

For you were called to freedom, brothers. Only do not use your freedom as an opportunity for the flesh, but through love serve one another. For the whole law is fulfilled in one word: “You shall love your neighbor as yourself.” But if you bite and devour one another, watch out that you are not consumed by one another. But I say, walk by the Spirit, and you will not gratify the desires of the flesh. For the desires of the flesh are against the Spirit, and the desires of the Spirit are against the flesh, for these are opposed to each other, to keep you from doing the things you want to do. But if you are led by the Spirit, you are not under the law. Now the works of the flesh are evident: sexual immorality, impurity, sensuality, idolatry, sorcery, enmity, strife, jealousy, fits of anger, rivalries, dissensions, divisions, envy, drunkenness, orgies, and things like these. I warn you, as I warned you before, that those who do such things will not inherit the kingdom of God. But the fruit of the Spirit is love, joy, peace, patience, kindness, goodness, faithfulness, gentleness, self-control; against such things there is no law. And those who belong to Christ Jesus have crucified the flesh with its passions and desires. If we live by the Spirit, let us also keep in step with the Spirit. Let us not become conceited, provoking one another, envying one another. Galatians 5:13-26

It should go without saying that we don't throw out any part of the Gospel in order to "reach more people" (because people don't like to hear about how they are sinners in need of a Savior), or to allow false teachings for the sake of "unity." (2Cor. 11:2-4, Gal. 1:6-10, 2Tim. 3:1-9, 2Tim. 4:1-5, Jude 1:3-23, 2Pet. 2:1-22, Acts 20:26-35, Matt. 7:15-20)