The relationship between a composer and his regular publisher is not one of employment. And publishers regularly refuse to work further with authors when said author does or says something that the publisher feels will make it look bad. Lawsuits don’t typically happened unless a contract has already been signed for the creator to provide a new work to the publisher, while if the two parties are currently between contracts, there are no grounds for a lawsuit.
That sounds like a lawsuit in the making, even if he wasn't a formal employee.