Nobody is arguing that space isn't big. The argument is space is big but dynamic, and launching enough stuff up there means that over a sufficiently long time horizon, you will have a collision between uncontrolled objects. This is not a theoretical concern, it has already happened [1].

Collision risk is significantly reduced by having maneuverable spacecraft with good conjunction prediction systems in place. But fundamentally, nothing is perfect and accidents can and do happen - you set a maneuver threshold based on an expected collision probability, but it's an engineering tradeoff: "spend the fuel to maneuver out of the way of everything, no matter how remote, or accept a small collision risk?"

And of course, when you are launching thousands of satellites, you will have a few failures that will become unmaneuverable hazards. Just the way it goes, you can't realistically engineer your way to perfect reliability.

So sorry, I have to reject your claims that it's "utter bullshit." Space debris risk is a well studied field, so much so that satellite insurance companies are starting to fold those calculations into insurance premiums. So yeah, it's real, and it deserves more than a pithy dismissal.

[1] https://en.wikipedia.org/wiki/2009_satellite_collision