We both believe that we should have faith. We both believe that we should obey the commandments. Where we differ is in how we are forgiven. For LDS they are forgiven by repentance which in the end means keeping all of the commandments. Christians also have a desire and belief that we should keep all of the commandments but our forgiveness in based on our faith in Christ for our salvation. We are justified by our faith. "Simply put, to justify is to declare righteous, to make one right with God. Justification is God’s declaring those who receive Christ to be righteous, based on Christ’s righteousness being imputed to the accounts of those who receive Christ (2 Corinthians 5:21).
http://www.gotquestions.org/justification.html
Should we continue to sin because we are justified by faith? Absolutely not. Paul addresses this common false ***umption in
Romans 6:1
"1What shall we say then? Shall we continue in sin, that grace may abound?
2God forbid. How shall we, that are dead to sin, live any longer therein?"
Should we confess our sins? Of course.
1 John 1:8-9
"8If we claim to be without sin, we deceive ourselves and the truth is not in us. 9If we confess our sins, he is faithful and just and will forgive us our sins and purify us from all unrighteousness. 10If we claim we have not sinned, we make him out to be a liar and his word has no place in our lives.
So we should not be involved in sin and we should not continue in sin. BTW this is a common argument given by LDS to try and support their position. But it is really a straw man argument in my opinion.