So now that the core principle is laid out, let's amend #2 to make it more like our example:
2) I buy a car that someone repaired with tools that he killed someone to obtain.
So, here as we add more aggravating circuмstances, making the crime in which we're participating materially more grave, so much more grave must be the justifying reason for participating.
Why obscure the matter, in order to make a more compelling argument for yourself?
We aren't discussing car thefts, but abortions:
ναccιnє #1: We obtained cells to test this ναccιnє by murder.
ναccιnє #2: We put murdered baby cells into the ναccιnє.
The use of the cells differs, but complicity in murder is integral to both (i.e., "Yes, I know you murdered a baby to test this ναccιnє, Please give it to me" versus "Yes, I know there are murdered baby parts in this ναccιnє. Please give it to me").
The moral complicity seems the same to me.
If you want to make the car theft argument, it is only an additional, supplemental, and secondary argument:
The real evil here is not unjust possession, but murder.