You know what they say about opinions . . .
A 1-inch telescope can show Jupiter's four largest moons, the planet's South Equatorial Belt and hint at the existence of a North Equatorial Belt:
A 1-inch telescope can show that Saturn is different and has "ears", or "handles", or a ring, or whatever:
A 1-inch telescope can show that Venus undergoes phases along with corresponding changes in its apparent diameter:
Only a blind person would say: "A scope under 7 inches aperture is of no use observing planets."
On the other hand, it's not the telescope that does the observing. It's sad and most unfortunate that some observers lack the ability to see and/or lack the ability to appreciate the sights that even the smallest of telescopes can reveal.
Is it just me who gets amazed and shocked when reading about new owners of 11-inch and 14.5-inch telescopes who have been unable to see some of the things that a 1-inch telescope is capable of showing? In light of that, I guess it shouldn't be so surprising to read that someone feels that at least a 7-inch telescope is needed for planetary observation.
. . . just another case of the blind leading the blind.