In today's Christianity, if you want to, you can very easily be a crusader against sin in the Public square. You can take up the cause against Abortion - something that is quite vile. You can take up the battle against Homosexuality and laws there about. Every few years there will be a call for a boycott of some place because they sell girlie magazines. I'm sure there are more active today...
In fact, American Christianity, especially since Finney and his focus on social change, has often been on one Crusade or another. You had the anti-abolitionists, you had the women's suffragists, you had the prohibitionists -- all fighting against an "evil" in society, all out to stop vice out there.
Now, for those of you who fight such fights with passion and zeal, don't take what I write here too harshly - but just as a friendly warning.
So often we define something grand and big as "sin". There - that is sin. Abortion - bad. Homosexuality - bad. Porn - bad. And they are... but that doesn't make other sin "good", or the things that tempt you less bad.
And here is the rub, here is where Satan will try to take down the most ardent crusader -- yes, you fight against Abortion. It does kill. But our Lord says that if you hate your brother, you are guilty of the same thing. Now, does your zeal against Abortion, which you do not do, let you ignore the hatred and anger you have in your heart? Or do you crusade against homosexuality or images, forgetting that the lusts of your own heart are just as wicked.
This is the danger - we can say "that" is bad, and we can be so intense that we forget or diminish self-examination. We can think of ourselves as a champion against sin instead of simply a poor, miserable sinner.
Christ our Lord says, "Why do you see the speck that is in your brother’s eye, but do not notice the log that is in your own eye? How can you say to your brother, 'Brother, let me take out the speck that is in your eye,' when you yourself do not see the log that is in your own eye? You hypocrite, first take the log out of your own eye, and then you will see clearly to take out the speck that is in your brother’s eye." Luke 6:41-42
This isn't addressed only to those really, really bad sinners who have big sins. This is addressed to each of us. My own sin is always bigger and more obvious than my neighbor's. I should be much more aware of my own lack, the ways in which I fail, than I am of my neighbor. And I am to constantly confess my sin, constantly receive forgiveness. Then you can... not fight a crusade against your wicked neighbors, but seek to show love and care and compassion for them, by aiding and defending them from sin.