Salvation and sin

I have been reading about the Reformation concept "Sola fide" (justification by faith alone), and I have a question for the WELS leadership. If one could become more lackadaisical with this mindset, knowing they would go to heaven regardless of following God's rules, what would your argument be against their thinking, other than appeals to emotion? I am genuinely curious about this, because I read in one post that 1 Corinthians 6:9-10 commands God's followers not to do a multitude of wicked actions, but wickedness and the baring from the Kingdom of God was due to impenitence. I suppose my question is ultimately, can a Christian be wicked, while simultaneously having faith in Jesus and being saved, since salvation comes about by being justified by faith alone, not actions, and if not due to the mere faith of the wicked, how would their disobedience to God's commands have denied themselves entry into heaven? To rephrase this in a less scrambled manner, how immoral can one be, with a 100% chance of being saved, if they espouse faith in Christ?

A starting point with your questions is to recognize from the Bible that Christians are saints and sinners at the same time. Those whom the Holy Spirit has brought to saving faith in Jesus Christ are holy in God’s sight (1 Peter 2:9). In spite of that gracious status, Christians do the evil that God forbids and fail to do the good God commands (Romans 7:15-25). As long as this earthly life continues, Christians will be engaged in a battle against their sinful nature that wants to lead them into sin (Galatians 5:17).

The question then is not a matter of “How much can I get away with and still be saved?” The Bible explains that Christians will want to avoid sin as best they can through God’s power and strength (Romans 6:1-4). God’s forgiveness is not a license to sin. Scripture is clear that mere familiarity with Jesus will not lead to eternal blessings (Matthew 7:21).

When Christians look to God’s law, they will see their sins and confess them (Psalm 38:18). When Christians look to God’s gospel, they will see the forgiveness of sins that Jesus Christ has won for them (Ephesians 1:7). In gratitude for that forgiveness, Christians strive to distance themselves from sin and, instead, live life God’s way (2 Corinthians 5:14-15).

In this life, Christians will never reach perfection when it comes to their repentance, faith and Christian living (Philippians 3:12). In this life, Christians are saints and sinners at the same time. They are people who enjoy forgiveness of sins because of their connection in faith to Jesus Christ, who lived a holy life in their place and endured the punishment of their sins. They are people who are engaged in the lifelong struggle against their sinful nature and Satan. The Christian’s confidence of salvation results from what Jesus Christ has done for them—not what they have or have not done (Ephesians 2:8-9).