Now, don't get me wrong, I'm not a big fan of the Catholic Church. Transubstantiation is a dumb idea. Its stance on contraception and homosexuality are self-defeating and mean-spirited. . .I really could go on. But that said, we live in a time where religion, and indeed faith, is being used to justify cowardly and hateful behavior. There have even been instances where legislators have tried to create loopholes in anti-bullying legislation for people acting out of religious desire.
Luther came to the idea of justification by faith alone by watching the Catholic Church use the "works" argument to justify all sorts of cynical behavior. For instance, for a price, one could wipe out a multitude of sins. Further, the Catholic Church figured out that as the key arbiter of what constituted a "good act" and a "bad act," it could justify torture, genocide and all sorts of evil. But at the end of the day, his belief that people strong in faith don't do bad things simply doesn't cut it. There are simply too many examples of people using faith to justify evil.
The most recent thing to stick in my craw is the latest Savage Love Letter of the Day. An evangelical family uses God and the Bible to justify its own hatred of a daughter and a son, both of whom are disowned. I am appalled, disgusted, and outraged. But here we see that once again, religion is used as a crutch to allow people to do terrible things. Little wonder so many claim to be "spiritual" rather than religious.
No, we have to justify people based on their deeds, not on their faith. But unlike the medieval Catholic Church, those standards of behavior need not be changed to suit our needs. Don't harm others (on purpose, at least), don't lie, don't cheat, treat everyone as you want to be treated. Give to charity, be respectful, don't be judgmental (that's God's job), etc. We'll all fail to be good all the time, but at least we won't rationalize our own failings onto God.