People undersell the meaning of Sim's decision here. This is the chronological seedling for why it makes sense that all Federation humans willingly use teleporters that clone and kill them, and why everyone on Voyager was so disgusted by Tuvix' selfish behaviour. Because even the clone of a primitive 22nd century man was able to overcome his desire to survive and die for the greater good - with the bar so raised on morality, it's inconceivable that any enlightened, evolved individual would ever do any less.