Here I stand. I can do no other.

(Thanks to Captain Spaulding for the idea).

Happy Reformation Day! On October 31, 1517, Martin Luther nailed a copy of his treatise on indulgences, later to become known as "the 95 Theses", to the door of the church at Wittenburg. And so began one of the largest movements of the Christian faith.
Martin Luther never set out to start his own denomination. He wanted to reform the Roman Catholic church, not leave it. But, once it became frighteningly obvious that the church as he knew it would not reform, he could not help but leave.
It's tempting, is it not, to go to church every week, and sit in the pew, and think about how nice it is that we certainly don't have to do that. Thanks, Luther, for doing all the hard work for us. Only that's not really true. There are still errors that crop up in peoples' beliefs. It is our duty and obligation to point out these errors and to help our fellow Christians (and non-Christians) to correct them. However, we should NEVER do this out of a sense of sanctimonious holier-than-thou superiority. It's not about "scoring one" on someone else, or making OURSELVES feel better because, hey, at least we're not like that guy.
No, it should always be in love that we do this. Because we CARE for someone and we are CONCERNED for them. This means, of course, that most of our "error correction", so to speak, will be a tadge closer to home than Luther's was. That doesn't mean it'll be any easier! Sometimes it feels far more difficult to try to point out the errors of a brother, a sister, a parent, a close friend than it would to try to...well...Reform The Church! And, while your relatives and friends probably won't try to cut off your head, they may very well cut off their relationship with you.
Wow, that hurts, doesn't it? Just makes you want to run right out there and start with the error correcting! Woohoo, let me at it - a chance to tick off my family, get them to never talk to me again, and have them think I'm a stuck-up, intolerant jerk because I am the one who said, "No, that's wrong, and I can't agree with that." It's very difficult to stand up - especially to family - and say, "I'm sorry, but I can't agree to that practice; it's wrong". It's even more difficult to follow that up with "if it continues, I'm sorry, but I cannot worship with you." But that's exactly what we are told to do in Matthew 18! If it's hurtful? Well, it's the pain that is supposed to help bring the erring person into line!
And what if it doesn't? We keep praying, we keep doing the right thing, and most of all, we keep loving them, and trying to help them. And, of course, we must be willing to accept error correction ourselves. None of us are perfect, and we will err too - so we must be willing to accept help in correcting our errors, as well.
It's also tempting to say, "Hey, that's between them and God, let THEM work it out." Unfortunately for us, God doesn't really give us that option. He told Ezekiel that if he appoints a watchman, and the watchman sees trouble and fails to warn the people, and they die, it's the WATCHMAN that's responsible. If the watchman does warn the people, and they ignore him, it's on their own heads. We are the watchmen. Each of us has been appointed by God to be a watchman for each other! God will hold US accountable for THEIR actions if we see them going astray and DO NOTHING. So if we see an error, it is our DUTY and OBLIGATION to point it out, and do everything we can to help that person correct it. And it is their duty to point out our errors, as well.
Even if it's family.
Even if it hurts.
Even if we don't like it.

Luther puts it best.
"Unless I am convinced by the testimony of the Holy Scriptures or by evident reason—for I can believe neither pope nor councils alone, as it is clear that they have erred repeatedly and contradicted themselves—I consider myself convicted by the testimony of Holy Scripture, which is my basis; my conscience is captive to the Word of God. Thus I cannot and will not recant, because acting against one's conscience is neither safe nor sound. God help me. Amen."

God help us all to do what is right. Amen.