It's not even my point that abortions should be banned because new DNA new person, since a lot of times we do things in the real world for practical not perfect reasons.

Like you have absolutists that say it's a new developing person so abortion is murder, but murder is subjective. Abortion is killing and there's a lot of killing of even full-grown people that society condones. For example, a lot of states have a Castle doctrine where it's okay to kill somebody even when you could retreat. Personally I don't care if a single cell is killed even though it's a new, developing person. Or a Down or rape baby, parents should not be forced to raise it.

But what the DNA argument does do is take away the idea that a clump of cells is not a person, making the ethical question one of murder vs killing instead of killing vs medical procedure / removing a 'growth'. A lot of liberals don't want to think of it as even killing, because especially convenience abortions would be a lot harder to justify.