Conflating full voting rights as a citizen with personhood is as bad as conflating personhood with the biological definition of life.

You don't make any progress this way. You're totally not talking at people who think that unborn babies deserve the same consideration as children.

I guess there is a small benefit of going, "Oh, you want to make a dumb argument? Well look, I can make a dumb argument in exactly the opposite direction!"

Pretty darn small, though, and it's doubtful it's part of the way toward finding common ground.

For that you need to listen, and to address people's actual concerns. (Also--some people are too intransigent to find common ground with. You need to know your audience.)