Pub-training: why it's bad and how to punish people for doing it

[[ID7]banready]

You'll often hear Moonmeander making fun of his enemies for pub-training.

Why is pub-training a sub-optimal strategy and how do you punish a team for doing it?

when I hear of "pub training", I think of a KOTF, Tempest, Defiler, Pollywog, and Forsaken Archer team that hit lvl 6 and start rushing towers together in a pack of 5, never leaving each other's side. I guess the idea is to knock down towers together and use their heavy AOE/team-fighting ults in unison if they get attacked?