We hold the right to vote in trust for children under the age of 18. In order to vote, they have to fulfill certain criteria. What your "logic" is implying is that we should be able to permanently destroy their right to vote because they haven't fulfilled those criteria yet, even though it is essentially a given that they will in the future. You want other examples of the government holding the rights of an individual in trust until they can be used, just open a damn book.
You're turning his point backwards and upside down. He is saying that a right in potential is not a right we give to anyone until they fulfil that potential. Voting is actually a good example, in that we do not give a 5 year old the right to vote because at some point in the future (s)he will have the right to vote. The right is withheld until a point in time when it is given. The 5 year old has no more right to vote as does a frog, or a rock. If that child is killed by an accidental car crash, for example, then it doesn't remove any right to vote because the child doesn't have that right yet.
Now look at the right to life, and imagine that the right to life is only given to beings who fulfill the criteria of personhood. Before those criteria are met, that being has no right to life, any more than we worry about a snail's right to life if we step on one, or a mosquito's right to life when we swat one. The question then becomes a simple one, when does a person become a person? Is it at the moment of conception, 1 month incubation, 6 month incubation, 1 month after birth, 1 year after birth? Is it separate from an exact timescale and based on some criteria like self-awareness? And more importantly WHY is it at that point.
Given the premise of the being in question being a human being with rights it is altogether reasonable for society and law to say, no you may not do that. That's my point. The way you shifted ground to cloud the issue with the fact that it was not proven is exactly the kind of dodge I always get. But don't worry, by the next page everybody will have forgotten and gone back to "teh bad peeple wanna control everbudy". Never fear.
The anti-religious sentiment is not based on the way in which religions seem to exert control (although there is a strong argument that no religion should even attempt to exercise any control through secular law over anyone who is not an adherent to that religion), it's based on the way they get to the definition of personhood as mentioned above. Arguing for or against something on scriptural grounds leaves no room for changing your opinion or of being persuaded by reasonable argument of the truth of an alternative viewpoint.
I'm happy if I lose an argument, based on reason, logic and proven reality and facts. It means I've improved my viewpoint to be more in line with reality. I'm not so happy if someone shuts down an argument with 100% certainty that they are right and nothing will ever change that, there is nothng on Earth that could be said or done that could possibly ever do so, especially when to do so they cite a source that I don't believe and have never be shown definitely matches reality (and I have been shown that in many cases actually doesn't match reality).