Hm. I noticed you seem to be defending your Wicca friend very strongly. Would you defend your Jehovah's Witness friend just as strongly? And what about your own personal faith? The answers to these questions will tell you a lot about how you feel about these friends, and about Christ.
You say these friends are very close to you; if they are so close, why do they not understand each other? This does not sound like something close friends do... so maybe they're not as close as you might feel.
That being said, if friends do not understand each other, they will never be able to make their relationship any stronger.
I recommend you sit down with each of them and tell them what Jesus Christ really means to you, and about his graceful and perfect Love. Read the Gospels in the Bible and listen to the testimonies of other faithful Christians if you need to; it will help a lot. Going to church does wonders, if you really listen to the message and seek God's guidance.
Once you know the love of God, you will be able to love your friends just as perfectly.
I honestly don't know what to do to stop the fighting. Each friend is probably very rooted in their ways and unlikely to change to accommodate each other.
Pray; and hope that God opens up a path to their hearts, if He has not already done so.
As for you, be prepared to encourage them to follow the Love that you have found.
"Preach the word of God. Be prepared, whether the time is favorable or not. Patiently correct, rebuke, and encourage your people with good teaching."
2 Timothy 4:2