I think when anyone stays concierge on repeats stays you develop a relationship with the staff, you even mentioned them all by name at the BWI. They get to know you, you get to know them, they know what you like, what you don't and that makes one feel welcome and comfortable.
Then you go somewhere you have not stayed before and you don't get that, because you are just one of many, unknown.
It's ok not to like somewhere you are not comfortable, but I think the perceptions were more from your view point than theirs.
Stay where you are comfortable. It's ok, others love the BC, so it all evens out.
I think this is why a lot of people suggest that when doing a split stay with a resort you are familiar with, and one you haven't tried before, to stay at the new one first. That way, if you like it, you will be going to another resort you like and won't be disappointed. If you don't like it, you know you'll be headed to one you do like when you make the switch. It's hard when you stay at one of your favorites, then move somewhere new, and it doesn't live up to your expectations.
Of course, the part about the "herd" is more the guest's fault than BC's fault. People are so concerned about getting their fair share (and then some) that they practically run over each other to do it. I'm sure that situation varies depending on the clientele staying at BC at any one time, since I haven't seen this as a chronic complaint for this resort. I'm sorry the OP, as a frequent WDW visitor, had to deal with such rude guests.
The staff watching the room can be hard to translate on a message board. I mean, they could be watching in case someone needs something, or they could be watching because they are bored and don't want to do anything else, or they could be waiting to pounce on a table as soon as it's empty so they can prepare it for more of the "herd". The OP would have the best feel for this because they were there to see facial expressions and body language that we can't see. It may sound like a trivial complaint at first glance, but it's all in how they were watching the guests, not the fact that they were doing it at all. I do find it apalling that a guest would not be greeted with a minimal "hello" when entering the lounge. I have to say I've stayed at BC frequently (not CL) and I can't recall seeing a CM and not having them greet me. If the regular CM's can do it, the CL CM's should certainly be doing the same.
And considering the proliferation of Coke products on property, I don't think requesting a Sprite Zero was out of line. I prefer soda with no caffeine after lunch time because I am very sensitive to caffeine and have trouble sleeping if I drink it late in the day. If the only diet soda available was Coke, I would have been asking for something else as well. If they didn't want to look, they could have just responded politely that they were out, or they didn't stock it, or something along those lines, instead of giving the impression that it was an inconvenience to be asked. People stay on club level because they expect reasonable requests to be fulfilled. Otherwise, why pay the premium?
I'm sorry you had such an experience there, and I hope the fact that you did check out and go back to BWI will be a catalyst for change at BC Club Level so other guests receive an improved product.