On Facebook, I have friends who are religious but not scripturally correct in their teachings. They do post things that are correct at times, but knowing they are in error on the whole, I am always questioning myself as to whether I should respond when they comment, or just try and teach them that what they are a part of is erroneous in its entirety. I am also wondering how to approach them given that most are women seemingly working their way to be preachers in the denominational world.
"If anyone speaks, let him speak as the oracles of God. If anyone ministers, let him do it as with the ability which God supplies, that in all things God may be glorified through Jesus Christ, to whom belong the glory and the dominion forever and ever. Amen" (I Peter 4:11).
When your friends get a point right, praise them for being accurate. If they didn't supply a verse, quote it to show that they are correct. When they get a point wrong, again quote the verse that shows they are wrong. Often I will leave it at the quote, but if I think it might be obscure in some way, I will add a brief comment about how this verse shows the point is incorrect.
You don't personally attack the person making the false claims, only the claims themselves. "But avoid foolish and ignorant disputes, knowing that they generate strife. And a servant of the Lord must not quarrel but be gentle to all, able to teach, patient, in humility correcting those who are in opposition, if God perhaps will grant them repentance, so that they may know the truth, and that they may come to their senses and escape the snare of the devil, having been taken captive by him to do his will" (II Timothy 2:23-26). In this manner, if they have an argument it is with God and not you.
Remember that when posting replies, it isn't just your friend you are trying to reach; you are also talking to all the people who overhear the conversation by reading their news feeds of friends of friends.
Finally, don't think you are only successful if the person breaks down and agrees with you. As I said, remember that you are also teaching many other people who haven't said a word. You don't know whom the Gospel will reach. Along with that, you don't need to have the last word. Make your point and if the person refuses to see the obvious, shrug and move on. If they ask for clarification, then of course respond. If they make new points (the distraction technique), answer the new point but know that the fact that they didn't respond to your rebuttal to their original point will stand out to other readers.
Like always I do sincerely appreciate your response. May God continue to bless you, your family and the congregation there. Continue in the work of the Lord. It's certainly the best work.