When John writes in 1 John 3:14 that we know we have passed from death to life because we love our brethren, he is not talking about how we know we have eternal life, but how we know we are in fellowship with God and one another.
Not everybody who calls themselves a Christian acts like one. The defining characteristic of Jesus was love, and so those who follow Jesus must also be defined by love. So we should stop calling ourselves Christians, and let others label us as one, but only if they see our love.
Is it a blasphemous thought to think that you hate God? Of course not! In fact, go tell God what you are thinking. He wants to hear it. Seriously. The last thing God wants is for us to shut ourselves off from Him. So if we are having blasphemous thoughts toward God, the best thing we can do is talk to God about them, so that He can show us how much He loves us, and how the God we think we hate is not actually the God He truly is.
Go burn in hell! Have you ever had anyone say that to you? I have. It usually comes from people who claim to follow Jesus. But this is not the Jesus I know. The Jesus I know hangs out with sinners and loves those who are rejected by the religious right. So if you tell a group of people you think are sinners to go burn in hell, you are saying the same thing to Jesus, because he hangs out with sinners.