1Pe 4:8 And above all things have fervent charity among yourselves: for charity shall cover the multitude of sins.
Some Christians are surprised that the Bible tells us that loving one another is the most important thing for us to do. But while you can make mistakes on doctrine, loving other Christians is never a mistake. Fighting among Christians is to be avoided. The idea that we have to warn others against a certain Christian is an excuse for disobeying God's clear command.
Nancy and I are members of a megachurch in Texas, and we watch our pastor every Sunday on the internet. We disagree with some of the dress standards of our church, but we don't disagree with the large numbers of people who are getting saved, nor do we disagree with the spiritual growth that we are getting from listening to our pastor. Because love is more important to us than a dress code, we aren't cut off from getting these blessings.
Don't go to war with every Christian you disagree with. Concentrate on loving one another, and trust God to handle the other problems.