Don't take this seriously. It's just a cruel argument.
Rather think of it as an argument that takes the same emotional liberties that atheist arguments against religion often opt for. IE nothing is sacred and that which you hold the most dear is actually meaningless.
How much do you love your children? Have you prioritised their well-being since day dot? Do you miss them when they're not around and would you give your life for them if faced with the choice?
You poor, sad and confused meatsacks.
Despite the most insurmountable odds, you were given an opportunity to learn about your world but instead you fell at the hurdle of biology and have never gotten up since. Your entire life has been devoted to a chemical equation that you have been able to do naught about but balance.
That deep love that you feel. It's not love at all. Your sense of connection is fake and the nature of your purpose is nothing but the result of a mixture of chemicals.
In reality, you are no different to a long time junkie. Dragged around by your nose with the promise of your next endorphine hit. Whether you inject heroin or jump through the hoops biology has set out for you to get your high...you are a druggie and in your case, your children and grandchildren are just the tools used to get your fix. And it makes you feel worthy, loving and like you have purpose. Like a good little machine should.
Your love for them is rooted in a handfull of chemicals that your brain gives you access to when you do little deeds that strengthen the odds of successful propagation.
What sad little creatures. "Feeling so deeply and loving so unconditionally". Do you actually think that it is love you feel?
Think about your children. Odds are, there is very little special about them. They're likely just run of the mill people that haven't contributed much to the world. Yet your chest swells with pride when you regale the world with tales of their mundane deeds.
The responsibility you felt and let guide your life since they first opened their little eyes is nothing but a carrot and stick. And you've been chasing that carrot "endorphins" ever since.
Remove your little chemical reward and what's left. I'll tell you. Nothing. Nothing but memories of when the feel good chemical still pumped through your brain. Memories that you translate as good times and righteous love. Memories of chemicals. Not memories "love".
But wait...what's that I hear you say..."my love for my children is more than chemical".
Oh, so spiritual? Esoteric? Energetic?
Well then prove it, you fucking junkie. Just like all chemically dependant losers, you'll find ways to justify your need. You'll go to the ends of the earth to prove to yourself that you need it. That it gives you meaning and purpose. That it makes you feel better. That it's how it should be and you are willing to sacrifice anything to get it.
Well, you can't prove it and since you can't... you are nothing and your children aren't much more. Then accept that your life is just as meaningless and pathetic as theirs no doubt will turn out be. Addiction, they say, is hereditary.
You "deep emotional connection to them" is nothing more than...C158H253N41O44S and it weighs 3463.013 Da.
You've wasted your time on earth by giving in to a chemical drive and then wallowing in addiction from that day on.
Sad, pathetic...meatsack.