They are probably talking about ecology. Where land bridges downsides are generally outweighed by the benefits(populations exchange genes more readily and move more readily). A land bridge does actually increase the flow of disease. The real concern though is fire. Which land bridges don't stop, but i fact help. Normally a highway would be a fire barrier and these crosspoints have to be watched like a hawk because of it. Science is often the complete opposite of intuitive and the reality is connected populations spreads disease and fire more readily. This person isn't necessarily insane depending on how they came to this conclusion. They're passing their ecology exam but this sub isn't. I don't think they are sayi9ng land bridges are bad necessarily. They just aren't perfect.. If they were a perfect solution there would be more of them. They're expensive though and tend to bring about a few different long term effects in the computer models.