This can be done safely if you know how to compute the correct wire gauge for the distance, and don't overload the circuit. You can easily and safely run 15A via a proper-gauge extension cord from a 3kW inverter to a fridge or any number of other individual appliances at once.
Where this is potentially going to cause trouble is people who don't understand how electricity works, or that different wire gauges exist, or how many watts various appliances use. The kind of person who takes a tiny lamp extension cord and plugs a power strip into it, thinking that more sockets will provide unlimited power.
The photos in this article are scary. A 2500W power strip with a bunch of crap plugged in? Exactly the kind of scenario you don't want to see. And talking about running a fricken induction cooktop off that, along with a fridge? The photo and text imply that you have near-unlimited power.