Trying to force more people to live in the absence of resources? You're basically still killing people, you're simply distancing yourselves from the act and washing your hands of the responsibility. Maybe the person who dies will not be the one who can afford longevity treatments; more likely it will be some poor bastard with a different skin color and hat in some distant foreign land. This doesn't seem to worry the people who believe that bearded men live in the sky.
The people who actually believe in the bearded man in that lives in the sky are indeed concerned about living conditions in the third world. That's why they're building wells, providing medical assistance, and working to end child sex trafficking. Admittedly, I don't have a faith based charity off the top of my head that deals with food specifically, though I'm sure that some exist. Point is, the Christians on the receiving end of your condescension certainly exist...but the Christians who are actually working to combat poverty and poor living conditions in the third world are too busy addressing those problems to try and market themselves at a volume that can be heard above the Westboro Baptists.
On the whole, it would probably be more humane to just have everyone in the world play Russian Roulette once a year and thin the herd by 1/6th annually. Oh, wait, that would offend the people who believe that bearded men live in the sky.
Two things here. First, your condescension is misplaced. I don't see how believing that life is valuable is somehow an undesirable trait. Don't get me wrong, I understand that it's common for Christians to place more value on a fetus than a death row inmate, but the abstract concept of "life is sacred" does not seem like a terrible stance to have. That being said, let's roll with your idea for a minute, and have an annual "Russian Roulette Day", where everyone has a 1/6 chance of being shot, because resources. Is it not advantageous for society to keep alive a doctor who won the lottery and heals the poor for free? Is that person truly an equal loss to society than a convicted serial killer? Either we run the risk of losing 1/6 of our core human infrastructure, or we start issuing 'exemptions' for world leaders and decorated veterans...and everyone else with money and/or connections to get on that list. As an added bonus, we know that the drug lords and mobsters aren't going to show up for Roulette Day, so a decade of this plan, and chaos starts getting ever closer to actually happening.
Better yet, don't kill anyone, and incentivize population control. Oh, wait, that would offend the people who believe that bearded men live in the sky.
While sure, many of the people who have absurdly large families are also devoutly religious, that doesn't necessarily make it a direct comparison. I'm fully aligned with the concept of removing all government-based fiscal incentives for having more than three children - got a fourth? Great. No tax deduction after the third, and you pay for schooling out of pocket. If you can pay for 'em, you can have 'em, but if someone is going to get offended by the requirement that the money come from somewhere, that's not something that religion alone is responsible for.
Maybe the best strategy is not to play the game (i.e. let people die naturally)? Even now we can prolong life medically for people that are effectively invalids and/or in chronic pain, but to what advantage? Many of them would be happy to be allowed to pass away. When medical care rises to the level that these people actually want to continue living, then maybe we can talk about longevity.
Death is not a bad option, really.
Personally, I'm with you on that. Plenty of people disagree with me, but I do believe that people should be able to make their own decision to pull their own plug if they want to - and can reasonably prove that they are competent enough to do so out of their own free will without coercion or duress, then go for it. Now, the problem of course would be truly proving it. If medical bills start piling up to the point where insurance is about to run out, and the person makes the choice to die for the purposes of not passing the cost on to their children...is that 'duress'? Those kinds of situations tend to get messy, but I'm speaking in the abstract here for a reason.