Firstly that's a 180 degree about face in your position, you claimed that Foveon sensors made all the difference between film and digital.
Secondly he IS wrong. Take a digital image, add the right contrast, saturation and curves, add grain effect noise and you'd be hard pushed to spot the difference between film and digital. You can take sublime photos on a cell phone, never mind a modern DSLR or film camera.
Thirdly the lack of an anti-alias filter is a cheat in any analogue to digital conversion (sound, images or whatever) as any detail above 1/2 the sampling frequency will produce false artefacts. Go look up Nyquist's limit, this explains the problem. The lack of the filter produces false lines and repeats when you get close to or above the limit on the Sigma. You don't get blotchy colour, but it's still wrong.
Distortions and noise are easy to add. Not so much to remove. A good camera system concentrates on getting as close to perfect as possible, and lets you do what you want with the images afterwards. There are many great photographers of the past who relied on the printing process and what they added there to lift their work above the ordinary. Digital makes this faster and easier.