Their literature teaches readers to hate 'apostates'. (Jehovah's Witnesses who leave their religion.) Jesus told us to love our enemies.
It's not up to Jehovah's Witnesses to warn and save people. Warning and saving people is God's business. He chooses who will be saved, not the organization. No one has no authority to command God and tell him who he must save or destroy based on their membership roster. ( See Organized To Do Jehovah's Will and 'the power to command God'. )
Jehovah's Witnesses have run ahead of the perfect Law of Christ. Bible clearly says, 'Anyone who runs ahead and does not continue in the teaching of Christ does not have God;' 2 John 1: 9 - 11 NIV. Read 141 Things Jehovah's Witnesses Can't Do.
Since the Law of Christ is freedom from rules and regulations, God has no need for an organization that judges Christians harshly based on doctrines Jesus didn't teach. True Christians do not judge on God's behalf.
God has not authorized any visible representative to take his place. The Watchtower admits in their literature that they are not inspired by God and they can make mistakes.
True Christians believe that Jehovah's Witnesses disrespect, belittle, and question the power of God to speak on his own behalf. God is perfectly capable of making his will known to all his people on an individual basis without any organized religion.
Jesus saves Christians. Any religion that tells you that following their rules and regulations is the path to everlasting life, does not have God. Jesus died so we can have life. Our salvation does not depend on the 141 things Jehovah's Witnesses Can't Do. There is nothing we can do to 'earn' eternal life.
Jehovah's Witnesses know idolatry is wrong. See Salvation. The Best Religion. Will It Save You? However they obey the 'slave' (the Governing Body of Jehovah's Witnesses) as if the slave has the authority of God.  True Christians are NOT devoted to any organization or religion. They are devoted only to Jesus Christ. For Christians, Jesus is the only path to everlasting life. John 6: 67 - 69
God's people give all their devotion and love directly to Jesus. They put their faith and trust in him alone. He speaks to them as they pray for understanding and meditate upon his Word. Jesus answers all prayers.
God warned Noah about the flood because Noah was a man of God. No religious group knocked on his door and told him to build an ark. Likewise Jesus loves and protects all people today who willingly choose to worship him. A representative is not needed to warn God's people and keep them safe. Jesus is able to speak to his loved ones on an individual basis if he chooses to do so.
1. 'The slave’s will is Jehovah’s will. Rebellion against the slave is rebellion against God.' Watchtower June 1, 1956 page 346. (Read new truths about the 'slave' Watchtower June 15, 2009 )