This is a common misunderstanding. Quantum physics isn't strictly about small things. It's about systems with a low number of degrees of freedom. Experiments have been done with "macroscopic" (thousands of particles) systems; in controlled conditions the system can be made to exhibit quantum behaviour despite not being what one would traditionally call quantum.

I think the misunderstanding on DBeumont's part here is that he's taking the idea of decoherence in macroscopic objects to mean that they aren't governed fundamentally by QM when it just means we don't tend to see that kind of behaviour on our scale.

There have been experiments done with high numbers of coherent particles showing that it is a matter of maintaining the conditions to allow for coherence rather then some inherent exclusivity in macroscopic objects or that they are somehow exempt from the predictions of the theory, as you say, you can derive classical physics from QM.

Particle-like behaviour is one aspect of the manifestation of energy in quantum fields.