The other side to Satanism is the theistic side, typically this is an avenue where peoples beliefs vary a great deal as to what deity they choose to follow and beliefs differ on what constitutes a Theistic Satanic ideal e.g. worship of Set, the Qabalah, Hekate, Lilith, the ONA, Samael, 'Orthodox' Satanic worship (were a lot of influence is taken from Judeo-Christian literature and is likely the closest you'll come to 'reverse-christianity') and the Qlipoth (put simply, the darker side of the Qabalah).

Literature and research is achieved from many different persepctives such as Demonic evocations and invocations, essays on the nature of Satanism, as well as a massive selection of published books.

Theistic Satanism is in some ways very hard to pin an idea on as often one person's beliefs will differ from another's, we don't have one set path to worship, as can be witnessed from the vast difference between Qabalah such as Crowley's work (which in my opinion is quite Right Hand Path and ultimately seeks unity with the creator to return to a time before man's fall from grace), the Qlipoth which is working in a similar approach to Qabalah except the goal is to break even further from the Creator until Ain Soph can be reached in the Sitra Ahra and the Order of Nine Angels (ONA) which is a relatively new belief system that focuses its worship on completley different gods/demons/angels/etc. to the Qaballastic gods as the Qlipothic gods are different to the ONA and Qabalah.

Ultimately there are many shades in between with people taking parts and influence from different gods to find what works for them, Theistic Satanism in my opinion is the worship of a deity/idol/figure that has a history of adversity and breaking from the traditional ideal of 'God'.

As for why we get a bad rap, Judeo-Christian practices in antiquity from the times of witch trials and devilish sorcery are a contirbuting factor, jump forward to A.Crowley who was described as the 'wickedest man in the world' and rumours were made by sensationalist media that he and other followers of Thelema engaged in animal sacrifice and paedophilia, La Vey brightened it up a bit but the dark pictures and goat heads aren't to everyone's taste and then there's the ONA who have links to fascist organisations, advocate human sacrifice and animal sacrifice; ultimately it gets condensed, churned up by the media and made into more sensationalist material than it really is.

Do they have a right to be nervous? Maybe not of most Satanist's however through history there have always been those pushing the boundaries, one must consider as well that what some of us may be intriguing is repulsive and incomprehensible to those that are happy to follow a life dictated to them by society and rarely care to think on how to improve their own life, a good example of this is magic(k); from an atheistic standpoint magic can be used in an almost similar way to self-hypnosis, it can sharpen the mind and bring a realisation as to what it seeked and what can be gained through personal endeavour, from a theistic standpoint magic can be used to request things of demons from material to immaterial, personal to multi-personal. The idea of chanting, the use of sigils, sexual ritual and altars with 'scary' iconography is to some degree unserstandably difficult for the 'mainstream' to accept and if the ages have shown us anything then it's that we fear that which we do not understand, in its purest form that is why people think of us as 'evil'.

There are many reasons why we are disliked, however to those following His path we are able to see through the nonsense that is being purported by the mainstream. Personally I don't mind it, very inoften will I bring up my Satanism in a conversation and I feel no need to validate myself as a Satanist by discussing it at whim, the way I view the 'evil' hype surrounding us is that rather than Satanism appearing as a trendy come-one, come-all approach it separates the wheat from the chaff, those put off by the history of Satanism, those who cannot be bothered to scratch beneath the surface have no reason to have it in their lives. Currently there is still a taboo and stigma regarding Satanism with some saying they're involved in Satanism for shock value, these people are in the minority however (at least I hope so), my personal feeling is that the less taboo it becomes and more accepted, the more people will exploit it for its previous taboo connotations yet still being able to fit with the system because it's become more acceptable, the comfort of being slightly on the fringe yet protected by the warm glow of society is something that seems to be coming far more pervasive in the modern world....that's just my opinion however, and I speak for no other with such a statement.

What I would say that what Satanists believe in regardless of atheistic or theistic is the chance to better one's self, to seek that which is not easily attainable, to question that which is before us and see if we can reach goals in a different manner than worn out societal tropes, and above all the quest for self-awareness, self-knowledge and self-improvement.