Firstly to be fair, this isn't supposed to be part of UK politics per se... and does deserve its own topic.
Secondly this is just a debate one that we can carry out logically but cannot perform in society as long as we possess rational empathy. Every female mammal possesses mother tendencies (depends on the hormone levels but it's a given for the most part) that the cry of a baby will evoke the response. We've studied this over time with multiple mammals (once again if memory serves me right discussed in The Naked Ape) and confirmed this.
Also are we really going to argue whether it is right to kill life outside of a womb? Abortion is one thing that's normal and fine since the right here isn't the right of the child but the right of the woman bearing the child. Here's the thing when it comes to these ethics, are we going to put aside individualism entirely? This question exists outside of the choice of the woman and enters the choice of the child, the ones that chose to bring it into this world and on a larger scope society. Therefore the responsibility rests on the persons bearing the child and/or responsible for the nurturing of the woman for those 9 months and fostering the urge to give birth to the baby. The Ethics should reflect that; equating it with abortion is muddying it and just trying to be inflammatory.
Now, when the child has no such responsible adults; it becomes, depending on the nation, either a property of the state, an individual that needs to find a home via the state or just a life that's going to be shunted from one foster home to another till someone takes the child in.
The argument that comes about here is, does everything that's perceived to be living then deserve to live? Should we kill every animal that's born which doesn't have a home because we have an abundance of them (cats and dogs easily come to mind). This argument isn't quite solid because it takes away a few things that we use to differentiate ourselves from our baser instincts and those are primarily - humanity and choice.
Of course this argument isn't new i.e. to kill babies and that they are blank slates. Not at all. But the thing is we aren't putting these children to better use when we can. Manpower is vital to society. Even if I were to side with them I don't get the point of killing the child. I mean manpower is vital, we could breed a new workforce in isolation. Breed in effectiveness a third world society to feed and make the mother/birth nation prosper. Wouldn't that be better than life on the streets. We do strip them of choice in that matter though. But if we're to kill them, then we strip them of choice once again. I'm against the destruction of resources and human labour has always and will continue to be one of the 4 fundamental resources in economics as long as we are humans. Utilise it in a different way. How killing babies is different from abortion is that someone has born the infrastructural costs in this case to give birth to one, it's upto the state/society to choose what to do with it. And this is while standing on the side that sees them as a burden to society.
As it stands this argument isn't new, and seems to be more of an exercise in argument rather than anything else. However even at that, it has some actual flaws since it's too focussed on comparing killing a new-born to abortion.