Some critics of Catholicism like to point out that Catholics are also divided. “Look here!” they cry, “You Catholics also have liberals and conservatives. You have homosexual priests. You have women pushing for ordination. You have New Age theologians and the majority of Catholics ignore Humane Vitae, don’t believe in transubstantiation etc etc.” 

Of course we do. These are called ‘bad Catholics’ or ‘dissenters’. There is room for differences of opinions and styles, but where it needs to be, the Catholic Church’s teaching is quite clear on both doctrine and morals, and when there is lack of clarity the Church is quick to clarify for the good of the faithful. There is room for difference of opinion and there is a hierarchy of truth–some truths demanding greater adherence than others. Clarity of teaching is available for all who wish to be faithful Catholics. Those who disobey the teaching of the Catholic Church do so either out of innocent ignorance, poor formation or deliberate and knowing rebellion against the authority they claim to follow.
Because the Church does not enforce uniformity does not negate her essential unity. There is an underlying organic unity to the Catholic Church which is like that within a family. A family may have rebellious members, sick or unpleasant members or downright crazy members. They might be an embarrassment, a nuisance and a headache, but they are still members of the family and an inner, organic unity still exists between them and their other family members.
The unity is preserved not by total, uniformity of belief and practice, or by complete and total obedience on the part of all her members. The unity is preserved because of the existence of a unified teaching authority and the universal pastor.
The teaching authority of the Catholic Church is not validated by the number of people who obey her laws any more than the validity of the Ten Commandments is validated by the number of people who keep them perfectly. In fact, the validity and need for the Ten Commandments is actually proved by the fact that they are disobeyed. When we see the chaos that results from our disobedience we see all the more how important the Ten Commandments are. When a person is killed by a car going 70 in a 30mph zone we realize why the 30 mph. speed limit is necessary.
Likewise with the teaching of the Catholic faith. Those who disobey and dissent only prove the wisdom and necessity of the Church’s teaching. It is this underlying unity and integrity which exists within Catholicism because of the unified teaching and the role of the universal pastor.
The dis-unity of Protestant sects, on the other hand, is total. With the lack of any unified teaching or any universal pastor each individual must become his own pastor. “We will not have a Pope!” they cry. What they really mean is that they will not have a Pope, for when there is not one Pope every man becomes his own Pope. So either have one Pope or millions.
When challenged on this matter Protestants are notably without an answer. When asked by what authority they teach, interpret the Bible or announce the truth on some matter they have nothing–absolutely nothing to fall back on except their own opinions based on their religious experience. 
This ‘experience’ is usually intellectually vacuous, sentimental, unsubstantiated with either facts or history, if Scriptural at all it is based on a few shallow proof texts and is as ephemeral as the emotion in a greeting card.