If you want to assume you can trust your network, so you don't need security in the hosts, you need to have a sysadmin who secures the network or have it airgapped directly. You can get rid of all of that, but then you must assume your network is untrusted and need to have security in every service you run.
I don't think switches refusing connection to devices that don't live there is a good analogy to "racist, xenophobic and homophobic".
Why not? The behaviour is kind of similar. The difference is that humans have an inherent right to live, while packets don't have an inherent right to be delivered.
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