He means you cant catch scouts with anything.Carriers are slow and you can at least pursue them.All you can do with scouts is wait for them to hit you.
They're called fighters. Unless the enemy is protecting those scouts with flaks and other unit types and such (in which case, it's NOT scout spam) you can use strike craft to knock them out.
With carriers, they warp in, kill some units with strike craft, kite a bit, then warp out before you kill anything. Still possible even in the current version, though mercifully much easier to counter.
The problem with scouts was that, with dedicated scout spammers, it killed any ability to tech up. If you never saw a game where it was basically impossible to tech up because of scout spam, you didn't play enough games.
At close proximity, maybe, but teching at close proximity is difficult regardless of what your opponent is doing. I often found myself able to scrape together 5 labs for heavies against scout spammers. Scout spam is also a great way to cover for teching, enabling you to hold together with low-level units while you bring out stronger ones.