...trying to claim that a person using the 'potential' argument should therefore seek to have every possible egg cell fertilized is ultimately a strawman.
It's not. Taking their rationale to the absurd, logical conclusion is a valid method of showing a flaw in thought and reason.
It is a misrepresentation of their actual position, based on what you think they should mean by it rather than what they actually do mean, and that makes it a strawman.
I understand what you are saying, but it's not. It is showing that they have made an argument for their position, but that they arbitrarily apply that argument when it suits them, and if they were to actually follow that argument, they would end up in an absurd place. We do this all the time with theists.
They say, "they bible says X"
We say, "yes, it does. but the bible also says horrible things Y and Z. So, the bible is no basis."
Or they say something like "demons cause cancer"
We might ask why they draw the line at cancer and not every other ailment?
They might say blah blah blah, objective morals.
I might say, why not objective table manners?
These are all taking their ideas to their logical conclusions to illustrate the point that their ideas are flawed. Az, I and others have pointed out that "potential life" is a stupid argument because "potential" can mean a lot of other things - ova, sperm, cloning, etc. That is not a strawman argument. "Potential" is not thought through. It is an undeveloped argument. If "potential" then why not ova, sperm or blood cells for cloning? What is the distinction? The approach we have used is a rhetorical way of bringing this up. So far, it has been answered with... what?