Rabbits, just like dogs & wolves have a pecking order. If the bunny is being charged at, it’s because it’s a newer rabbit or a younger bun that hasn’t learned it’s place yet. Rabbits rarely attack another rabbit just to pick on it (rabbits are not spiteful), so it all has to do with finding ones place among the family. With bunnies, it”s all about learning. The older rabbits feel it’s their duty to keep everyone in line so you will see them display some charging, ears dropped back, nipping & kicking behaviors as you introduce new bunnies into each others territories. Territories may include ones special corner of the house, feed bowls, toys & blankets. Some bunnies will even get jealous of a new rabbit if it’s laying next to you & they haven’t approved of that behavior yet. Aren’t bunnies silly? I just love them! 
Never allow bunnies to “fight” with each other. They can really harm each other, tearing open bellies, biting genitals & causing nasty wounds with their bites. Some bunnies will fight until death so watch them closely as you introduce new ones to the family warren. Always be present until all buns have formed solid bonds & all aggressive fighting has stopped.