As an engineer who designs products, and a guy who likes to port saws, I still find it reasonable for a company or individual to decide to use only stock saws. I would only buy a ported saw if I knew the work had been done by a couple of individuals, and even then it would depend on the model. And I would never sell one of my modified saws, as I know what real product development entails and I know I have not done it.
Certainly not every product design is equally good - doing a better job than the competition is what puts food on my table. All designs are compromises that must meet a whole lot of often competing requirements and constraints, many of which a particular operator may not care about - and this is where the opportunity for performance mods mainly comes from in that those uninteresting constraints can be discarded. So one can increase noise and emissions and fuel use for more power.
Still, by the time a saw makes it to market it has been through a lot of testing for durability and safety, etc. That's simply out of the realm of possibility for the small shop porter. The design and development resources of a saw manufacturer are so vastly greater than any porter will have.
Regardless of that though, there's no excuse for acting the way the guy did, although it is so common in the US any more.