(Note: Please be sure to read the comments to this post - there's more interesting information there, some of which contradicts what I wrote. Dave)
There's an article doing the rounds at the moment that's trashing Trader Joe's Charles Shaw wines. Personally I didn't think there was a need to; I find they vary from poor to undrinkable myself, and won't have them in the house. But some people will drink anything - look at how much Budweiser gets sold every day. I'm not going to link to the publishers; that just encourages them.
However the article contains a good deal of misinformation which really deserves to be addressed. I should point out that I haven't visited the
factory winery myself, but there are some things that are common to just about all facilities, from the smallest to the most industrial.
Are there rats, birds and insect bits in the wine? Well, rodents don't tend to live in vines 3 feet off the ground, and if they did they'd certainly get out of the way as soon as a tractor came close. Gophers tend to be the biggest pest in vineyards; they live in the ground and attack the roots, not the fruit. Similarly with birds; in fact most winemakers net their vines to prevent birds from getting access. The odds of wildlife getting caught by the harvester is very small indeed - but not zero.
No winemaker that I know of, even at the highest level, will search through the grapes to ensure that there are no insects or frass present. It's just not going to happen. Some wineries have what's called a shaker table - it's effectively a long tilted metal table that vibrates. The vibration moves the grapes from one end to the other. Insects and other detritus will typically fall off in the process; the whole clusters will move through to the crusher-destemmer. Top wineries will have human sorters who will remove any leaves and clusters that don't look healthy or ripe.
Wineries that need to process large amounts will still need some kind of conveyer system. Bugs will have plenty of time to get away, but obviously some won't.
Having travelled along the conveyer the clusters enter the destemmer. This is a rotating drum with holes in it; the grapes fall off the stems and go through the holes. Very unripe grapes will remain attached to the stems and come out of the other side. If a bird or rodent did make it this far it will be ejected too. The grapes then fall through into a crusher that breaks the skins, and from there are transferred into the fermentors.
So it's possible that a trace of animal material can make it into the bins. And as I said, that's true of just about every winery I know. It's also true of just about every food production method I know; that's why there are legal limits on the amount of foreign matter allowable in just about every food there is; it doesn't mean it's necessarily there, but it does mean that the food isn't considered to be contaminated by it. In the case of wine however that matter will get removed when the wine is pressed - and if for any reason it didn't, then it would be removed by the racking and filtering. that goes on when the wine is finished.
The article also states that the wine is sweetened with grape juice and sugar. Well there is nothing illegal about adding grape juice to wine - if there was then Tokaj, one of the world's greatest sweet wines would not exist. Adding sugar is illegal in California - as is adding water except under certain circumstances - but why would you sweeten with sugar when you can use grape juice? (The adding of sugar is called chaptalization, and is permitted in some countries when the wines don't have enough fermentable sugar to start with. )
There are plenty of legal additives such as
Mega Purple that wineries can use to improve the perceived quality of their cheap wines. They don't have to disclose them, though some wineries have started to and I greatly encourage that.
So while I don't encourage anyone to drink Two Buck Chuck if they can possibly avoid it, there's no reason to believe the false claims being made against it. If you really want to avoid something nasty in your diet then look out for partially hydrogenated oils - that stuff is seriously bad for you.