As one who has personally observed a few leftists in their natural habitat, I’ve documented two distinct types.
The first, a naturally insulated genotype, whether by circumstance or by result of intentional intellectual self-segregation, exhibiting an infantile insecurity in their own belief system, which manifests as an abrasive and oft hostile xenophobic tendency towards other-minded individuals, is typically atheistic out of pure ignorance of all theism. They do not bother themselves with socially acceptable norms for “morality”, as they have no regard for social acceptance outside of their insular social puddle of amorality.
The second, typically a former centrist, right leaning, or apolitical breed, too distract by their own virtue signaling to focus on morality and reality, do everything in their power to fit in with their newly found leftist circles, lest they be perceived as a centrist/right leaning thinker and be cannibalized by their new peers. Driven by a bitter resentment towards anything associated with their former philosophical belief system, they self-ostracized from their prior social circles either fully or partially (the reason for their partial withdrawal typically being due to a subconscious nagging guilt, or to not lose their financial dependence on said prior social circle). Despite having no logical connection to the cause of the trauma inflicted within the prior circle, any philosophical agreement is a painful association, in a PTSD sort of manifestation, and must be dissociated from fully. This breed is concerned with morals, but is willing to live with the cognitive dissonance to support their self-ostracization, viewing it as a justifiable means to an end. Traditional definitions of right and wrong and morality at large are not viewed with the widely accepted centrality-to-life, but as an auxiliary factor that must be sacrificed for the subject’s own mental health, as they are simply doing what they can to survive their own past emotional trauma.
It is standard for both of these categories to lash out at anyone seeking to define them as unoriginal or fitting into a mold, despite them being unoriginal, and fitting into a mold better than a bunt pan pound cake, sans frosting. It is also expected for them to refuse all logical arguments regarding theism and to lash out emotionally when confronted with logic. Somehow they self define as spiritual but not religious, and not believing in any known God, despite not typically spending any serious amount of time studying Theology with any serious level of breadth and depth. They take their lattes with soy, and pumps of various chemically processed foreign flavoring agents.