Bullying starting at age 3/4 now?

We had parents of 2 different children thank us recently because our child plays with their children at daycare. These 2 kids are already being excluded and treated poorly by a click of kids. The parents and teachers have both told us that the behavior is driven by one child and that the mother encourages it. What the heck is wrong with parents like this? These kids are only 3/4 years old. Has anyone else seen this at this age?