You're probably being downmodded because half a pound of weight is not a major feature, but you're trying to shoehorn it into a trump card. For me, the trackpoint mouse is a
major feature which leaves the Air dead in the water, but it's really a minor feature between the two.
Same as all the extras that the X220 has over the Air, like card slots, swappable batteries, and a perimeter that doesn't cut into your hand. And vice versa. These things are all minor differences. The Thinkpad laptops are also as tough as the Apple laptops, if not tougher - despite looking like a normal laptop, they survive more military tests than 'hardened' brand laptops.
The short version is simply that the Lenovo X-series and the Apple Airs are equivalent laptops at the same price point - the Air is not 'better' for 'less' than the 'inferior' product.