Refuting heresy and rebuking those who spread it is commanded by the Bible, and there are plenty of examples in the Bible of it being done.

Read Jude, 2Peter2,Galatians 1v8-9,Matthew 23… where in scripture is loving your enemies ever applied in such a way that teachers of heresy are not to be rebuked?

Rob Bell is an enemy of the gospel, a wolf in sheep’s clothing.