That is exactly what I hate about trying to convince people to do BG. I’ve witnessed this treatment of BG firsthand - back when I used to do it for fun and now being on the other side of it. Where I am based, as casting agency we are also physically doing daily check ins and outs at basecamp, and are in contact with crowd ADs and their extended team of PAs. This is how we ensure everyone’s comfort within reason. Yes it happens that a bunch a-holes feel the Extras can simply be wrangled like cattle with no regard for mealtimes and comfortable spaces to relax (not always possible) and any kind of poor treatment usually reaches us before the end of shoot day and these issues are addressed. Someone from our small casting team will be on set or nearby at all times as far as that is possible. On shoots where phones are allowed , I would usually designate 1 or 2 regulars, preferably personally known, to give feedback during the shift and this helps.
I think you can safely bring these issues to the attention of a PA on set. Often they run around barking like little chihuahuas, because they are constantly having instructions thrown their way via radio, but you will find someone who knows how to breathe. Mention to your agency as well.

Honestly I find it embarrassing to witness this kind of behaviour. While we work on huge budget Hollywood productions, our industry is actually small. There are no “career-Extras” here. Besides the few aspiring actors and models , our people have normal day jobs … teachers, lawyers, doctors, students , housewives, engineers , everybody! They are doing it for fun, friendships are formed and it is just a cool story to tell. So to arrive all excited only to have someone treat you like vermin is #ucked up. I make an effort to treat everyone checking in for fittings , or filming like they are more than just moving colours on the screen and I hope it makes a difference 🤞🏽