Lucky cat gave an excellent answer on the subject.
It seems that whenever someone wants to perpetrate evil onto others must give reasons and pit one thing versus another.
Though there are extremists in all types of groups, political, religious etc. there are also those who really look at things in a detached unbiased way.
Using an unwilling being for whatever purpose we consider "useful" or "good" is wrong period. Note, i said unwilling.
If i were to force my love upon you, or another who is unwilling to accept it, though it is Love, it would still be wrong.
You have to give consent.
This question is aimed mainly towards animal right activists that contest the experimentation on animals (in my opinion) and would lead to the reply "so if your mother were ill etc etc"
the matter of the fact is that if you have to declaw, debark, anaesthetize an animal to do what you will, it is wrong, just like using date rape drugs, or taking advantage of someone who is passed out, or a child that can not defend him or herself.
I think we can all understand this.
One thing is to quickly kill an animal for food if that is one's nature another is to make it endure pain and suffering to study it no matter the motivation.
Were someone we love to pass on, would we want it to be quick and painless or long and suffering? I surely would not think "I hope he suffered and died in pain or he could do nothing about it while someone was "using" them".
There is one beautiful saying, hard to live by and yet most profound:
Truth shall set you free.
As long as we find excuses, lie to ourselves, lie to others for whatever reason, to be accepted, not to feel alone, for our own advantage, we shall never rid ourselves of the evil within.