You took that out of context
"God does not work salvation for fictitious sinners. Be a sinner and sin vigorously.... Do not for a moment imagine that this life is the abiding place of justice; sin must be committed."
You took this out of context... Here is the complete saying of the above quote... "If you are a preacher of mercy, do not preach an imaginary but the true mercy. if the mercy is true, you must therefore bear the true, not an imaginary sin. God does not save those who are only imaginary sinners. Be a sinner, and let your sins be strong, but let your trust in Christ be stronger, and rejoice in Christ who is the victor over sin, death, and the world. We will commit sins while we are here, for this life is not a place where justice resides. We, however, says Peter (2. Peter 3:13) are looking forward to a new heaven and a new earth where justice will reign. It suffices that through God's glory we have recognized the Lamb who takes away the sin of the world. No sin can separate us ...