When I was in my High School debate class this type of argument would make me beam with joy. It is the type of argument where you need only a passing understanding of the topics in order to tear it to shreds. It involves gross oversimplifications and generalizations that display true ignorance and is worth reading just so you can join in on the comment thread. Hopefully sending the message to Scientific American that posting this kind of drivel won't fly.
To be clear I do not blindly hold heirlooms to be the perfect plants without flaws. I think their are plenty of heirlooms that aren't worth growing in my climate or would do worse than modern hybrids. I've grown both types of seeds and continue to grow a mix. That said I believe this article is complete rubbish for dismissing heirloom varieties, and more specifically non-GMO varieties wholesale.
This was my response to the article:
There are around two-hundred dog breeds recognized by the American Kennel Club. There are many hundreds more recognized tomato heirloom varieties. To boil that diversity down to a single false comparison is lazy and shameful. The better question on the comparison is how do you think dog owners would react if Monsanto said they were going to replace all of their feeble and inbred dogs with a genetically perfect dog? Would you describe dog breeders as archaic and backwards? Would you so easily dismiss the unique qualities of all those breeds?
The section on genetic diversity is also bordering on ignorance. Heirlooms don't have better or more genes than other tomato plants, they just have different variations. It is the combinations that make them special and unique not the number or quality. To discount the variety that can be obtained from just 10 genes shows a complete lack of understanding of genetics. Each gene can have multiple alleles which can provide many hundreds of thousands of combinations with just a handful of genes. A similar number of genes leads to all the many cat coat color types for instance.
At the end of the day the article attempts to make a subjective choice and objective one. To do that this article selects the worst possible examples and applies them to all heirloom tomatoes. In the end I want the variety of tastes that come from the many heirloom varieties I grow, not something with a comparable sugar profile.