Man's life is both an end and a means to that end. I've seen this fact given as evidence that it is wrong to sacrifice others, but I don't understand what the reasoning is that leads to that conclusion. Why does the fact that man's life is an end in itself lead to the conclusion that one shouldn't sacrifice others?
When it is said that "man's life is an end in itself," which men (i.e., people) are included within the meaning of "man"? If the claim is, "My life is an end in itself, therefore I should not sacrifice others to my ends," the missing step should be clear: failure to include others within the meaning of "man," treating "man" as applicable only to oneself. I wonder if the questioner is unclear about who the concept "man" subsumes.
Also, "man is an end in himself" is not an axiom or self-evidency; it is a conclusion from more fundamental observations and integrations. For the Objectivist validation of "man is an end in himself," refer to VOS Chapter 1 and Galt's Speech in Atlas Shrugged, reprinted in FNI. (Excerpts can be found in The Ayn Rand Lexicon.)
Update: End in Itself
In a comment, the questioner seeks further clarification of the relation between "ultimate value" and "end in itself." This is answered in the topic of "Ultimate Value" in The Ayn Rand Lexicon:
An ultimate value is that final goal or end to which all lesser goals are the means -- and it sets the standard by which all lesser goals are evaluated. An organism's life is its standard of value: that which furthers its life is the good, that which threatens it is the evil.
The Lexicon entry on "Standard of Value" is important to understand, also:
The standard of value of the Objectivist ethics -- the standard by which one judges what is good or evil -- is man's life, or: that which is required for man's survival qua man.
Regarding the issue of how to deal with others, including whether to sacrifice others to oneself or not, the Lexicon entry on "Trader Principle" explains:
The principle of trade is the only rational ethical principle for all human relationships, personal and social, private and public, spiritual and material. It is the principle of justice.
If one accepts the principle that being sacrificed to others is evil, why wouldn't one also accept that sacrificing others is also evil? Sacrifice is sacrifice; evil is evil. One does not achieve virtue by doing evil.