I think Alvy Ray Smith understands both the fundamentals of sampling theory and the practicalities of real-world image synthesis and display, given his role in the creation of computer graphics.
Re "If they [displays] did [filtering] then anti-aliasing wouldn't be a thing" - that doesn't match my understanding of sampling theory. If the computer graphics process of image synthesis has folded down high frequencies in the hypothetical source signal, well above (half) the image sampling resolution, so that they now overlap with lower frequencies of the image -- i.e. the image generation suffers aliasing -- then no "filtering" downstream (at least in the traditional signal processing sense) can undo that, and the shape the display elements certainly won't save you either. The job of anti-aliasing is to prevent high-frequency energy from landing in the band-pass in the first place.
Re "plenty of cameras don't have any filtering": the physical act of counting photons that fall onto the areal extent of a CCD element (with an the associated directional distribution created by the prior optics) is absolutely a filtering of the incoming optical signal. That is independent of any subsequent digital filtering of the pixel data.
Re "If they [displays] did [filtering] then anti-aliasing wouldn't be a thing" - that doesn't match my understanding of sampling theory. If the computer graphics process of image synthesis has folded down high frequencies in the hypothetical source signal, well above (half) the image sampling resolution, so that they now overlap with lower frequencies of the image -- i.e. the image generation suffers aliasing -- then no "filtering" downstream (at least in the traditional signal processing sense) can undo that, and the shape the display elements certainly won't save you either. The job of anti-aliasing is to prevent high-frequency energy from landing in the band-pass in the first place.
Re "plenty of cameras don't have any filtering": the physical act of counting photons that fall onto the areal extent of a CCD element (with an the associated directional distribution created by the prior optics) is absolutely a filtering of the incoming optical signal. That is independent of any subsequent digital filtering of the pixel data.