Jesus was judicious and perfect in all His words, speaking with perfect divine wisdom. But He didn't instruct us to be satisfied that we are perfect in our words before we tell others the gospel. We should do the best we can with the help of the Holy Spirit. Speaking up is important.
I would rather have a blunt ax at work than a sharp ax in a museum. Better than both is to put a sharp ax to work. Meaning: better if we are more prophetic in our evangelism - but not so prophetic that we never speak up and tell people the gospel.