Religion is in some ways a force for good, but it can also be a very negative force in the world.
In one way, religion is very good for us because it tends to help instill good moral values in people. I am not saying that only religion can instill moral values, but it is certainly one force that can promote such things as justice and human rights.
On the other hand, religion can be the cause of horrific conflicts. Once again, it is not that religion is the only source of terrible conflict, but we cannot deny that things like the Thirty Years' War were caused in large part by disputes over religion.
Overall, one could argue that religion is generally good for individual people but that it can create problems when it is used as a reason for mass actions such as wars.