There are no "sectlets" in the Catholic Church. The Faith of the Church is the same everywhere, for all time. There are different emphases on some aspects of the Faith from rite to rite within the Catholic Church, as well as different emphases on certain doctrines. But the entirety of the doctrinal deposit is acknowledged by all, and the different emphases represent a healthy diversity based more on culture than anything else.
But I suspect you don't have that so much in mind. What you doubtless refer to as "sectlets" take their shape in the arguments - almost exclusively in the West - between "liberals" and "conservatives" that all western Christians plainly see in the media on a daily basis. I would state that this is not quite the intradenominational battle that it seems to outsiders. The fact is that western liberal Catholics invariably hold to one or more doctrinal aberrations that the orthodox Catholic would consider heretical, that is, not part of the teaching of the Church through either Scripture or Tradition as explicated by the magisterium (the teaching authority of the Church). In this sense, these folks are not really Catholics at all; they merely haven't the social graces necessary to just *leave*. Even Luther came to the point where he knew whatever he wanted to "reform" couldn't be accomplished with his own continued presence in the Church, and he had the sense ( in a human way of looking at it) to leave.
The large majority of those people you hold up as examples of "sectlets" within the Catholic Church are simply neo-Protestants who do not, or simply will not, own-up to the fact. They are facilitated in this by a Church hierarchy that, for reasons that almost always escape the likes of myself, does not think it expedient to formally excommunicate them. They are, in reality, no more a part of the Catholic Church than you are yourself, though they do not share your own intellectual honesty about the fact!
To the extent that such people do not recognize the God-given authority of the Catholic Church to preach the Gospel authentically as the "pillar and ground of truth," (1 Timothy 3:15), they have cut themselves off from it just as surely as Luther, Calvin or Knox ever did. For orthodox Catholics, they are not our responsibility as "Catholic sectlets"; as Cafeteria Catholics, they are the embodiment of what St. James had in mind in James 2:10. With the current pope, I believe that they will see, in short order, that "the cafeteria is closed!" As will be your argument.
Oops! "...some aspects of the Faith..." in paragraph one: "Faith" should be "liturgy."
The liberals in the Catholic Church should be called Neo-Protestants because their spirit is Protestant, not Catholic.