Feeding raccoons is not a good practice for several reasons. First, raccoons can carry canine distemper, rabies, roundworms, tapeworms and other viruses that can be fatal to humans. Second, it attracts more raccoons to an area than the area would normally support and puts the animals in close contact with each other. This can cause the spread of disease between the raccoons. If the neighbor refuses to stop feeding them, you can call Animal Control, explain the situation, and request that they pick up the animals to be euthanized. Other options would be to call the Illinois Department of Natural Resources district wildlife biologist. Or to hire a nuisance wildlife control operator to remove and euthanize the raccoons. You can find contact information for the IDNR biologist at:
http://web.extension.illinois.edu/wildlife/professionals.cfm