The Bible uses colourful language

Just a quick one here. Some Christians think that Christians should never use "colourful" language in debate, as it is unhelpful, or unnecessary or can cause offence etc.

Granted that:

1. Christians should never use crude or filthy or foolish language, Ephesians 5:4
2. We should use wisdom to judge our circumstances, consider weaker brethren, etc.

But yet, actually the Bible uses colourful rhetoric, especially in refuting false doctrine. Potent weapons must be wielded carefully - but forbidding use of them especially in such a good cause is definitely wrong. How can we fight without potent weapons?

Here's my example. What does Paul think about those who are so keen on circumcision? He wants them to go the whole way!

I wish those who unsettle you would emasculate themselves! - Galatians 5:12