Adding oxygen to beer once fermentation begins WILL OXIDIZE your beer. That said, some beers are actually suited for oxidation - like barleywine, imperial stout, or some strong ales. Oxidation during will likely add a sherry component to beer, which is often desired in stronger, higher-gravity beers. But it does NOT belong in most beer and steps to avoid oxidation are warranted.
In other words, The Bruery
intentionally oxidizes their RIS to add to the flavor and depth of the beer. It "works" because they WANT that flavor there. So I'd make sure that the sherry component is actually desired in your beer before you go introducing oxygen to primary. If you're making an Imperial IPA with 8%+ alcohol, you should not be introducing oxygen because the off-flavors caused by oxidation are undesirable in that style. IOW, don't go solely by your ABV but by the flavor profile of the beer. Old Ale? OK. Barleywine? Sure. Imperial Kölsch? Not so much.
And FWIW, I think most serious homebrewers have already been "shaken up" by John Palmer, Jamil Zainasheff, Ray Daniels, Greg Noonan, George Fix... those are the names I think most homebrewers have on their shelves these days. Including a dusty copy of Joy of Homebrewing.
(and occasional mentions of RDWHAHB
)
phew, I feel better now.
As for aerating must, I've been looking into this as well. A few people on here have said that simply shaking your carboy will both expel CO2 (which it will) AND aerate the must (which I don't believe). Since CO2 is heavier than air and is trapped in the headspace & neck of the carboy, how could O2 get "sucked down" into the carboy? The simple weight of the CO2 would prevent that from happening (and is precisely why purging kegs with CO2 is an effective way to avoid oxidizing beer when you rack it from carboy to keg).
So I don't know how a lees stirrer or shaking (or any method other than compressed O2 or an air pump) would work. Anyone know?
I promise the beer part of this post came out way more cranky than I really intended it to and I've tried to nice it up a bit but I clearly have an opinion on the matter, lol.