First, it is a known fact that almost all conspiracy theorists are barely capable of adding, let alone multiplying and working with squares. Ask to see his math. I would bet anything he will balk and try to bluff his way through.
Second, tell him atmospheric density is measured in kg per cubic meter, or pounds per cubic foot, and not PSI. Drag formulae use density, not pressure.
Third, parachutes don't need a "certain" density to inflate; they need a gas blowing into it to inflate.
Here's the real math:
Mars' atmospheric density at the surface is about .02 kg/m
3. The density scale height is 11.1 km. At 100 km the density is about 2.4461e-6 kg/m
3.
So at 100 km,
30,000 mph (13,411 m/s),
a parachute coefficient of drag of 1,
a parachute diameter of 10 m (I don't know what it was. 10 meters seems reasonable for demonstration purposes),
and a spacecraft mass of 3893 kg,
would generate 4.4 m/s
2 of deceleration. That's about half a g.
To rub more salt into his wound, tell him meteors burn up at an altitude of around 80 kilometer in the Earth's atmosphere. The density at that altitude is equal to the density of the Martin atmosphere at an altitude of 71 kilometers.