Saying that Haiti was leveled because of the people's evil is true in a sense, but I think most people who say this think that they are somehow better. It is only because of God's mercy that any of us are spared. God would be perfectly just in obliterating all mankind from the earth because all people have rebelled against Him. Besides that, even Christians suffer, but that does not mean that they somehow did something to deserve it. Christians suffer persecution, are disciplined by God, and refined like gold in a fire, and this all entails pain. There were Christians who died in Haiti along with the wicked. There are churches in Haiti enduring great hardship there right now, but I am certain that God will work through them because of this suffering and they will be stronger as a result. Already I see God working in Haiti. The corrupt Haitian government is being scrutinized and may even be reformed and the North American churches have mobilized to bring aid to the people, along with the Gospel.
As for the voodoo part, I have heard that voodoo is common in Haiti. Voodoo is derived from African rituals that witch doctors and shamans would perform and was brought over with the Africans when they were enslaved by the Europeans. Here is a story I heard personally from a missionary to Haiti that our church supports:
The missionary travels on a boat around the island, preaching in the towns and then pulling out from the shore at night for security reasons. One night, a voodoo celebration of sorts was being performed in one of the towns he was at. While on the boat at night, he could actually feel it when the evil spirits were called by the people - and he was not the only one to feel it. At first it was very still, but then all the animals in the area started making a huge racket as if they were all afraid of something. The evil presence moved through the area and converged on the town. The missionary spent the night in prayer and reading the Bible. There was no way he would have been able to sleep. The experience was something he would never forget, but it also steeled his resolve to help the people and preach the Gospel.
I hope that provides some perspective on the Haiti situation. It is easy to think that we are somehow better because we are prosperous and there have been few disasters where we live, but that is wrong thinking. We should, instead, support Christians who are doing something about the disaster, whether it is providing shelter, medical aid, food, or the Gospel.