You've got it bass-ackwards, thinktwice. Marxism, and the resulting Leninism and Stalinism, was based on a 'morality,' in which certain things (collectivized farming and wiping religion from the face of the Earth, as examples) were believed to be 'good' and certain 'bad.' In fact, these 'good' Leninist notions were considered to be far more good than not committing murder. As a result, very intense reason was brought to bear in carrying out Marixist morality. You use the word altruism to mean doing anything someone claims to be good for others (by any morality). Thus, because Marxism intended to improve the world, you are able to label 'altruistic' the massacre of millions. You think that Ayn Rand's ideas are good for the world. Thus, her ideas must be 'altruistic' by your reasoning. Well, that's semantics at that point. The primary difference (besides the fundamental one about the belief in God) between Christianity and Leninism is this: Leninism used its morality (its idea of what is good and bad) and rationality to attempt to improve the world by brute force, the individual be damned (or murdered). Christianity posits a very definite morality (from God), and expects each person to strive to achieve to live life according to that morality. The secondary effect of that would be a wildly better and more loving society - but not brought about by force.
Speaking for myself, I use the word altruism to identify the ethics of sacrifice within Marxism, Naziism, Fascism, Socialism, and Christianism; and ... altruism is in fact the ethical bond those isms share.
The evil element in altruism is the mandatory self sacrifice demanded from individuals within Marxist, Nazi, Fascist, Socialist and Christian circles.
There is nothing immoral in voluntary self sacrifice, the insidious evil wrapped in altruism comes when nations, states and churches demand "sacrifice" from individuals.