First of all, for the response of that particular quote of Russell, I’d tell you to read
this.
Second, that argument is hardly valid, if at all. On the first note, most pro-choice people don’t believe in a Heaven, so their minds don’t rest easy on that point, and that’s used to who is actually trying to protect the babies. Second note, where is the confirmed claim that aborted babies go to Heaven? Last time I checked, either that or a sort of Limbo is no more than a theological theory, and that’s not to be taken for granted either.
Third note, our ultimate purpose is live here on earth as humans, not to respond to the universal call for holiness which gives us Heaven. That’s after our life here is done, and that should come when the life here is accomplished. Things here on Earth are much different than in Heaven, and it’s only after being here that you can really appreciate to go up there. Fourth, much linked to my thrid note, not even a baby can know true happiness without knowing true sadness in life, that’s just how human beings are built on.
Fifth, once again, it goes against one’s right for life. I’m not guessing you go around killing people that want to go to Heaven faster. You simply live your life as God wanted you to be in order to be clean and holy and able to enter Heaven. Any conception of a baby has the Original Sin which doesn’t even have the chance of being baptized, so you can’t really say you’re doing anything ok. Becoming holy is available to anyone that chooses to do that, and you’re not giving the baby any chance to do his own choice (yes, there are those who feel satisfied to have a short but intense life, and they’d rather not live an eternity; deal with it), and start and work on his/her relationship with God to truly know Him and being ready to meet Him. So, arguing that the baby is granted to go to Heaven is way too much of a bet. Most likely he/she’ll spend a lifetime in Purgatory to get ready to meet his/her Creator, which didn’t even had a chance to enjoy His creations by his/herself.
On the last note, and I don’t want to sound like aggressive or anything but really, how in the world do you even think of suggesting that?..