In other words, it's Catholic doctrine that it's objectively just as wrong for a Protestant or an atheist to support abortion as it is for a Catholic to do so. (The non-Catholic may be able to argue that their subjective guilt is mitigated somewhat by ignorance, but objectively the crime is just as wrong.)
Jenkins' excuse actually means that he is acting and teaching in defiance of Catholic doctrine on this matter.
To get real philosophical, wouldn’t all Protestants be “dissident Catholics” on some level?