I'm supposed to think about this before the first lecture.
How does cloning work and why do people get mad about it?
As Miss Oly K. said its the question of ethics. What would people do with clones? Can you imagine?
The first thing would probably be to implement them in war or for use as test subjects. The question is of their humanity. Are they humans? or are they just clones? I think the upset comes when people begin to face their own ethical assumptions/or lack of them. (what they would do with a 'cloned' life, when really its a human life)
But I am ethically biased for protecting life.
1) People get upset about cloning because they think scientists are playing God (or Allah or Budah or whatever higher power one believes in). Many believe that scientists or doctors do not have the right (and should not have the power) to create new humans (or dogs or mice).
2) People also belive it is very dangerous and that it may lead to a uniform human race like Hitler was trying to create. Or possibly that only positive traits will be cloned and then those with negative qualities will be even more looked down upon.
There are lots more......
I assume you're asking about artificial reproductive cloning, since people don't usually get upset over cloning on smaller levels (cellular or molecular). Reproductive cloning is done by taking an ovum (egg cell) from the surrogate (who will be implanted with the clone) and inserting the nucleus of a cell from the original animal to be cloned. This is given a current pulse to fuse them into one cell and implanted back into the womb of the surrogate.
People get upset about cloning, especially when the discussion is human-related, because there are ethical issues to creating an exact duplicate of someone. While some people argue the theological/philosophical side of the implications of an "artificially created soul", scientists also point out that clones tend to have shorter life spans, which means that if you created a duplicate human, he/she wouldn't live as long as he/she should, and would be prone to more health problems.
There are also some people who argue that you're wasting the potential life in the ovum from which you are replacing the nucleus.