Most people are motivated by moral arguments in their choice of political ideology or issue or simply party. "This is right, this is wrong." For whatever reasoning they subscribe in defense of that moral stand.
The appeal of Marxism follows that pattern -- for the followers. They subscribe to the moral stand claimed by Marxism -- a variant of altruism, including egalitarianism. Where Marxism diverges from the pattern of standard moral appeal is in what else it seduces people with.
Marxism seems almost unique from other ideologies in that it offers a systematic intellectual justification that directly appeals, on a wide scale, to one specific personality defect: megalomaniacal power lust. Not only appeals to, but cultivates that trait in followers.
Moreover -- and this makes it infinitely worse -- Marxism is designed to appeal to intelligence: neurotic intellectuals, riven with doubt about their abilities or ideas, turning them eventually into psychotic corrupters of the truth and the young.
What could be more insidious?
The moral argument of the alleged "rightness" of egalitarian "social justice," which is the core of the broader appeal of Marxism, is predicated on a unique twist over other evil ideologies such as Nazism: Marxism starts from condemning injustices by a class of people (creators and the most productive members of society) to empower the least creative and least productive, by cultivating a sense of entitlement where it doesn't exist -- feeding on and growing a deep resentment for anyone better, more able, more deserving of the fruits of living by having earned them.
This turns the followers of Marxism from advocates of "justice" (however warped) into destroyers and killers who are animated by one emotion: hate.
What makes it unique is that Marxism / Socialism / Communism retains the moral cover of helping everyone by enslaving everyone. This is a tremendously powerful rationalization for the psyches of the power lusters, because they need the rationalization of morality to justify widescale murder in reality.
No one can go through each day thinking "I am a worthless, evil human being" -- except for a true psychopath, which is the final stage of complete detachment from reality in the cognitive development of this type of person--if they don't commit suicide first (being killed fighting your enemies is a form of suicide).
But the main point I wanted to make here is that Marxism is uniquely a system designed to appeal to people who are predisposed to delusions of grandeur and power lust, who feel they are entitled to rule over the rest of us -- the ultimate form of entitlement, and the form that all "entitled" people eventually devolve to.
Marxism is designed to appeal to this trait on a mass scale. It's almost as if Marxism was designed to seek out all the psychopaths or potential psychopaths in society, and provide them the moral rationalization they need for killing, destroying and ruling.
With that moral rationalization in their gun hand, the shrunken corpse of their self-esteem becomes a Frankenstein's monster of inflated pseudo self-esteem, dedicated to eliminating anyone of genuine self-esteem, by any means. As long as they exist, they are an affront to the monsters, and their inflated sense of superiority leads them to concoct no end of schemes to achieve their ultimate end of ruling, to prove they are the only ones worthy of existence -- by eliminating all those who are genuinely worthy of existence.
Think about that again: a system dedicated to finding and cultivating psychopaths who seek to rule us, by means of rationalizations that prop up their own delusions of self-worth, while deluding all those whom they would rule that they are entitled to do so.
Try applying that lesson to understand some of those around you. How does it apply to, let us say, Barack Obama, or, in a more interesting way, to Michael Bloomberg?
But pick others -- pick nobodies, people you might know personally (not as friends, necessarily), and ask how the message of Marxism not only appeals to their self-doubt and anger, starting from the moral argument of alleged "justice", kindness, enforced charity, good-deed-doing, whatever, and how that person might evolve in time to desire to rule and destroy others around them.
Then take it full circle, and ask how the moral arguments of Marxism -- if not the label itself -- appeals to genuinely decent, normal people you know, and how those people support the other kind of people -- the megalomaniacs -- based on the arguments of enforced charity, kindly benevolence towards the unworthy, and the God-like omniscience of The State.