I'm not familiar with Thornless Honey Locusts, but my farm has both Thorned Honey Locust and Black Locust. They spread like nobody's business, and you can't just cut them down b/c they will then grow as suckers off the root stock, let alone the main stump. Currently, we are girdling and spraying the cuts on everyone we run across which is everywhere. My grandfather stopped cutting the farm's fields about 20 years ago, and all of our pastures are becoming a mix of cedar and locust trees. My uncle was just cutting them down without spraying, and he started a mess that we are now having to correct.
Your cousin is correct, the deer and birds eat the pods. In our case, the bad outweighs the good of food - there is plenty of other good trees such as oaks, persimmons, chinquapins, etc that aren't a problem like locust trees.