The problem with some crew at BA is that thy totaly live in a 'BA bubble world' and can be a bit oblivious to the airline world around them.
They tend to have only flown for BA, or flown for BA for years. Seeing/married to someone else that works for BA. Only use BA for staff travel. Etc etc. Often, I don't think it is that some of them 'look down' on other airlines, more so that they are a bit ignorant to the airline world outside BA.
I remember when I was on my initial training course with BA and you have these regular little 'reviews' with your customer service trainer. This old girl (my trainer) was BA through and through. "So have you flown before, Keeperboy?" She asks. "Yes, I flew for BMI and Virgin" I reply. {Confused look on her face} "Oh yes, BMI, thats like the low cost airline from that....what's it called....Midlands, isn't it?" I reply "No, it is the airline that used to be British midland that has now re-branded itsef BMI". Then next question. "so, why did you leave Virgin, Keeperboy". I reply it is mainly a money thing. "oh, I thought all airlines paid pretty much the same" she replies. I tell her how much a 5 day HK is worth at VS. She laughs, thinks I am joking.
I kid you not, some of these people (even in BA training) are just so oblivious to the outside world it is incredible. So, if someone at BA looks at you curiously, don't take offence.
And if they don't talk to you when you are a passenger in uniform don't take worry. MANY a time I have commuted in my BA uniform on a BA flight and not been acknowledged as 'one of us'. It is just the culture though. We have 14,000 cabin crew, and at LHR anyway, it's usually a group of faces on the flight we have never clapped eyes on before.