There are now people, maybe a majority of Bitcoiners, who genuinely believe that spinning up non-mining nodes helps secure the network. How do we undo this?
Non-mining nodes do help secure the network in a number of ways:
  1. They improve privacy for everyone, by increasing the k-anonymity set of Bitcoin nodes.
  2. If needed, non-economic nodes can be quickly turned into economic nodes by changing wallet settings.
  3. They make it harder to perform node-level Sybil attacks, especially in circumstances where the attacker needs diverse IP address space.
  4. Running a node helps people learn more about how Bitcoin works.
  5. Running nodes normalizes running Bitcoin nodes, pushing back at narratives painting nodes as "money transmission" or similar nonsense.
  6. Publicly accessible nodes help other nodes stay in sync by providing bandwidth. This is particularly helpful if you run an archival node, especially with block filters turned on.
If you've got some spare hard drive space, you should run a node. It doesn't even matter if it's publicly accessible or not. Bitcoin Core is just software. You can run it on your laptop just fine (a pruned mode needs just ~10GB of space). I have Bitcoin Core on all my laptops and desktops.
If you have some spare money, go ahead and buy a raspberry pi or a mini-PC and run a node full time. At worst you'll learn a little bit about Linux and system administration, which is always a useful skill.
There are literally people now wasting time and money running multiple non-mining nodes in their basement thinking they are contributing to the network.
Yes, multiple nodes on one internet connection doesn't help others much, if at all. But very few people are doing that, and the few who are aren't significantly harming anyone else. This isn't a problem worth complaining about.