There is very little proselytising by Satanists. We do not expect or try to convert people. We do not want most people to convert to Satanism. Of all the Satanists I know, none have been converted as a result of a fellow Satanist convincing them that Satanism is right.
Satanism is not for everyone and Satanists are almost in unanimous agreement that Satanism should be repellent and confrontational enough that most people do not accept it. Although the world may become more Satanic, not many will call themselves a Satanist. There are only a very few Satanists who believe that anyone can be converted through proselytisation and persuasion. Most Satanists believe that a person needs to darkly embrace Satanism of their own accord and without pressure.
There are various routes by which people come to know of Satanism in a way that facilitates conversion.
Anton LaVey said many times that Satanists are born, not made. Testimony to this is the large number (the majority) of Satanists who did not need to be taught Satanism, who did not need to be converted, tutored or schooled in Satanism in order to comprehend it. Many Satanists, upon coming in to contact with the items in the above list instantly convert. The most frequent testimony of conversion to Satanism is "I read "The Satanic Bible" by Anton LaVey (1969) and I already believed everything it said, so I called myself a Satanist".
It is rare that a person struggles to accept Satanism. Many Satanists auto-accept as soon as they come in to contact with our philosophies. This is not to say that you must experience this in order to be a Satanist, but it is common.
This is perhaps one of the reasons that there is little proselytising in Satanism. If a person does not convert after being shown the basics the chances are Satanism simply isn't for them. There is rarely any point in trying to convince a person to accept Satanism if they do not automatically understand it. Proselytisation of those who are not born Satanists feels like a waste of time. Satanism is understandable to non-Satanists, but non-Satanists will not in general be converted through knowledge or understanding of Satanism and will rarely understand the attraction of the symbolism of our patron saint. Whatever demonic traits a person needs in order to accept Satanism seem to be more nature than nurture. Born, not made.
Other religions have experienced mass conversions and instant conversions. The rapid expansion of Christianity in history was facilitated by a large number of rapid conversions. Many adherents of all religions simply fell for the religion almost instantly upon learning of the religion. I will not attempt to understand this phenomenon, but merely do not wish the reader to think that I am claiming only Satanism experiences instant conversions.
Neophytes are faced with some problems. For some there is no doubt but for a few there is an issue of practicality. Some people are happy to never tell anyone that they are a Satanist. Some only reveal it to a very select few. Some Satanic evangelists are happy for everyone and anyone to know their affiliation. New recruits to Satanism are faced with the question of whether they can reconcile the potential social turmoil of religious conversion with their own openness.
Some people cannot emotionally hide such an important affiliation as Satanism and know that they will not be able to resist revealing who their demonic icon really is! Some people are happy to hide it -- for these conversion is easier. For those that can't, sometimes it is an insurmountable barrier. If you can't utilize the social effects of calling yourself a Satanist, or hide it, then perhaps Satanism simply isn't for you.
I can only think of a handful of people who I know who have de-converted from Satanism and ceased calling themselves a Satanist. So I will not say much about it. Some Satanists become disillusioned with the actions of fellow Satanists. Personally I don't care how other Satanists act. I will reprimand and instruct them just as I would any person.
Some people deconvert because they do not see the point of calling themselves a Satanist. I believe this is the most valid reason for deconversion. If you feel it is a detriment to your emotional well being then deconvert. Easy. Get on with your life. It is not Satanic to hold on to something that hinders you, if it is something that needn't be. 'Do not complain about anything to which you need not subject yourself'2. Ironically it can be Satanic to not call yourself a Satanist. Some people find the contradiction between individualism and identifying themselves with a religion to be too great.
Individuals who reject the Satanic religion probably fall into the following categories, in descending order of worth:
Have no need for religion, dogma or religious symbolism. I approve!
Have a distaste for Satanic imagery. Fair enough.
Are tainted by society: Herd mentality leads to prejudiced opinion that Satanism is wrong no matter how sound the underlying philosophy. The sheep.
Are closed-minded and ignorant, and refuse to learn or change. The hardcore untermensch.
The last entries are unwanted people, the untermensch, the lower kinds of people, the weaker, and would actively be shunned by Satanists even if they did mistakenly convert.
Satanists are born not made. This was LaVey's teaching and it is also the conclusion I draw from my experience of Satanic "community". Whether hidden or public, conversion to Satanism is for most people either irresistible or impossible. Not many struggle. If a person needs to be consoled or pressurized into calling themselves a Satanist then it is nearly always a mistake to call them one. This is why there is no proselytisation. Conversion is frequently through exposure to "The Satanic Bible" by Anton LaVey (1969) or the Church of Satan in the media, and via a few other Satanic books.
Gilmore, Peter. High Priest of the Church of Satan (as of 2001+).
The Satanic Scriptures (2007). Hardback. Compendium of texts. Published by Scapegoat Publishing, USA. Many essays are new editions of older texts by Gilmore.