All you have done is present your own defintions of certain terms, and then using those definitions justify your comparisons. If that was an acceptable move, why couldn't I just do the same thing? Why should your definition carry more weight than mine? Especially as my usage is the accepted usage.
1. Because we wouldn't be talking about the same thing. Reductio ad absurdum tactics require using the same definitions. (As does any counterargument)
2. No definitions have really changed. In every case, we are citing the behavior or the fetus in contrast with the behavior of a parasite. Parasite still means parasite. Fetus still means fetus. The comparison itself doesn't actually use different meanings of the word. People are arguing that a fetus behaves like a parasite (by the scientific definition).
A foetus has many more characteristics that distinguish it from a tumour than it does similarities, which is why it is a lousy analogy.
Can you name one of the characteristics and explain why it was detrimental to omit it? Preferably other than its potential to become a child, since we are already covering that below.
Secondly, the scientific definition includes difference of species. It's a crucial distinction, because bearing offspring is a crucial part of most animals' reproductive cycle. One can make the case for abortion without resorting to emotive and inaccurate language.
What makes that a crucial distinction?
When only considering its current behavior and lack of sentience, I find it more emotive and inaccurate to consider it under guise of offspring. Associations of children evokes human imperatives and protective emotions that relentlessly value our own species over others.
It wouldn't be a comparison if the fetus was actually classified as a parasite. However, since that single deviating aspect is irrelevant, why can't the sentiment associated with the original definition still function?
I know of no analogy that doesn't let the subject deviate from what it compares something to by an irrelevant difference.
Because the "deviating aspect" is the only one that actually matters. The comparison is only used for its pejorative value.
The value of a fetus is under examination.
If parasites are not valued because of their behaviors, why is examining that similarity a fallacy?
My point is simply that there are lots of acts which affect other people to no greater extent than abortion does, yet we do not think those acts are "okay".
If you'd like to extend the notion to other facets, be my guest. If I recall, suicide was an issue, and I happen to think people should have a right to commit suicide. Euthanasia, or otherwise.
Shortened to remove redundancies.