That is a complex thing to explain.
You see, many Brazilians do indeed describe themselves as Christians despite picking up a bit of Umbandist practice, most notably that of offering flowers to Yemanjá at the turn of the year.
Allow me to illustrate with my personal experience. Back in the 1970s I lived in Rio with my relatives. IIRC they were mostly deeply lapsed Catholics with strong Kardecist influence, with the odd LDS thrown in for measure. I don't think any of them was nominally Umbandist or Candombleian, although I can't be sure; those relatives of mine did not like to talk very openly or very often about religion, except for the period of time when a few of them would not shut up about Kardecism despite my begging. (That is a common attitude among Brazilians, by the way. In the urban centers at least it is considered slightly rude to make a point of stating one's religious beliefs without being clearly invited to.)
Even so, at least once at the turn of the year they decided to dress in white and bring me to the beach with them at the turn of the year. They even handed me a few white palm flowers for me to put in the sea water myself.
I don't even know whether any of them believed in the existence of Yemanjá. I suspect most of them do not know either.
You probably know already that in Brazil Yemanja has been melded with Mary mother of Jesus. There is a degree of controvery on how proper it is to consider them one and the same. Some people are bothered by that syncretism, but that rarely if ever leads to anything more than brief harsh words.
These links give a fair idea of how it is. Would you agree that it resembles a Hindu Puja?
Rio celebrates the goddess Yemanja
Offerings to the Sea Goddess Yemanja
Anyway, about the fights... perhaps the best way to explain it would be to present a few typical (or is it stereotypical?) religious profiles, somewhat slanted towards the "Carioca" community.
Most significant in purely demographic terms are the Catholics. If you have no other indication and have to guess, assume that a random Carioca is a Catholic who do not always think too much of religious matters. It is not a given, but quite possible, that he will have a smattering of Kardecist and/or Umbandist beliefs thrown in for flavor. He will usually try not to question other people's beliefs without a clear reason to. He may easily even avoid mentioning or asking whether other people even have religious beliefs in the first place, or he may feel that what truly matters is that people believe in God.
Then there are the Protestants, who come in various "flavors" but all tend to be at least a bit more overt about their belief in Christ. Some of them are discreet, others dress in stereotypical"believer" garb (long skirts or short sleeved social shirts with neckties, mostly). A vocal minority among them are "noisy" and sometimes end up passionate when faced with evidence of non-Christian beliefs (or lack of same). Incidents of attempts to shame or even threaten Umbandist temples have happened, albeit (and fortunately) few and far between.
Kardecists are common countrywide, and many of them see themselves as the natural and logical extension of Christianity, or even of Catholicism specifically. A somewhat rare dissidence follows Roustang (sp?), who is considered by many to be the reincarnation of Muhammad.
Umbandists and Candomble believers are fairly common, but they tend to blend in very discreetly in most situations. It is very rare for them to attempt to make converts without being invited to speak their minds on their beliefs. They usually are very respectful of the diversity of beliefs.
LDS are not uncommon in Brazil, and tend to be easily recognizable at a distance (they often walk in pairs, with white shirts, and name badges of a rigorously defined style). They are almost without exception also very nice people once one learns to negotiate their proselitism, which is hardly ever rude in the first place.
A minority that has become very visible are the Ayahuasca worshippers, not all of which consider themselves worshippers or believers as much as users.
Brazil also has a perhaps surprisingly high number of adepts of "Osho" Rajneesh's doctrine, which is a leading form of the current wave of "new age" beliefs. Also a heartwarming variety of Shinto derivatives, most notably Seicho No Ie. And a variety of Hindu and Buddhist schools and study groups. There is even a Sikh Temple somewhere in São Paulo, which I hope to someday visit. For a while now I have wanted to participate in
Langar, helping with the cooking if at all possible.
