This is the most common question we open air preachers are asked by the Christian community. Isn't the gospel about love and forgiveness and peace? Why do we often times look angry, downright hateful, and why do we confront people in such a way that often provokes a violent response? Why, in short, are we so confrontational?
For one thing, the very act of preaching publicly is considered by most to be shocklingly confrontational. Most people are not used to, let alone comfortable with a preacher suddenly breaking out in public to confront them in their sin. The very act of lifting up your voice to preach is often interpreted as "yelling" and disrupting the mood. When preaching, it is helpful to remember that the controversy you are bringing will help to draw people to hear the message you bring.
One must understand that this message is inherently confrontational. If you witness or preach and you do not receive a negative response, you might need to question whether you are preaching the right gospel. When you tell a large group of people that they are headed on the wrong path and if they do not change they will pay for it by burning in Hell, generally people are not going to appreciate this. Most sinners are careless and happy in the way they are leading their lives. When you preach the truth, which opposes their selfishness, and bring conviction upon them, you interrupt their happiness, and awaken these sinners to their rotten state. A happy sinner is not going to like this and will resist it in any way he can.
Granted, sometimes we open air preachers say and do things that are controversial even among other preachers. Sometimes, the Ruach Ha'Kadosh uses this to bring conviction on particularly hardened hearts. A barb of sarcasm or firm rebuke will often help to break a sinner. YahShua certainly was not a stranger to sarcasm or public rebuking. He used both. Not to mention the Prophets. The greatest Scriptural example of sarcasm would be Elijah and the prophets of Ba'al. He publicly mocked Ba'al and their religion, humiliating them in front of thousands.
The trick, of course, is not to be confrontational in the flesh, but to be confrontational in the spirit. Often the Scripture alone is enough to confront a sinner and bring conviction. Remember, though, that a sinner is not a victim, but an active enemy against Yah, and must be treated as such. Confrontational evangelism can be the most honest form of evangelism a sinner has ever encountered.