T.S.
Nicole, listen to Gail and Nicole! These moms who say you're hurting him by taking him off the team obviously haven't seen a real bullying situation unless their child is the one doing the bullying! That's not meant as an attack, but he's only 7 for goodness sakes and shouldn't need his fun time to become a time of anxiety. AT ALL. It's your job to give him skills to deal with his emotions and their words and actions, but also to protect his developing self esteem and sense of safety. Usually there's multiple teams w/in a community and if practice hasn't started for you then it's not too late to call the coordinator to request a switch of teams. If you don't he likely will learn to hate soccer and not want to join next year.
If that's not an option then maybe having the non-leaders over to play a few times, even if just one of them, could give him a little back up when the group is together. You likely wouldn't want to have him friends with the leader anyway if the parents are the same way. Eww. Getting with a child psychologist/counselor may be most beneficial to give him positive methods to deal with their behavior as well as his own anxiety.