Several research groups around the world are attempting to perfect techniques for growing animal flesh for human consumption, without requiring the killing of a complete intelligent organism. This is known as in vitro meat. Vegetarian groups are reportedly generally in favour of this development, deeming that this flesh does not constitute a living organism making it morally acceptable (see e.g. Wikipedia).
Following the same logic that would allow a vegetarian to eat in vitro animal meat, would it not therefore be morally acceptable for anyone to eat in vitro Human flesh, since this would not require the killing of a person?
Update in response to comments: Many (not all) vegetarians like(d) eating meat. They find it tasty and the eating of it pleasurable but abstain from this pleasure on the basis that inflicting pain and death on another organism to derive this pleasure is immoral. I have not tasted Human flesh, however it may well be very tasty and pleasurable to eat (if the object can be divorced from the concept of where it comes from, as is often argued is true for a lot of modern meat eating humans). If in vitro meat became a commercial reality, could making, selling and eating a Human flavour be morally defensible, since it doesn't require the death of an identified individual?
Note that eating a Human who has died accidentally is, in most but not all cultures, considered morally unacceptable because of the importance of ceremonial burial. We tend to care about what happens to the physical remains of our loved ones after their death.