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come2ireland - the travellers example was just an example of unjust prejudice and is off topic (though, for the record I feel you have over-simplified the issue), though the issue of treating people as a group rather than individuals is relevant: I think its probably harsh reality that if a bouncer has an issue with one member of your group then they may take issue with the group as a whole. However, I often find that where one of a group is refused access, the rest of the group can still go in without them. The main issue here, though, is how the bouncer makes the decision to refuse that person entry in the first place - it should not be discriminatory. If it helps to simplify the point, then maybe take the example scenarios I gave above and change them to 1 person, rather than a group of 3. Are you another that agrees with those above that its ok for a publican to hand-pick the people they let into their pub based on how they are dressed, what they look like and what accent they have?
Csider - you mention that rightly or wrongly the above will happen. I agree that it is happening, though it is wrong, unfair and (until someone informs me that the lawyer that told me about this was wrong) illegal, and so should not be allowed to happen.
In relation to your question "In the above example what extreme social grouping would you be more comfortable in being around?" I would be just as comfortable around either group. In my experience, those from wealthy backgrounds are just as likely to get into/cause trouble as those from working class backgrounds. I choose the places I go based on the style of the place, level of service, quality of the Guinness (actually this is the highest priority!).
That said, I rarely feel strongly on where we drink (though I try to stay away from places that charge way too much) and so I generally let the people I drink with decide: my friends are likeminded and are at ease with people from all social classes, though I find people from work (which is a fairly high paying high-powered kinda thing) base their decisions very strongly on what kind of person will be there. A 'kip' in their mind is generally a place frequented by working class people, and the actual physical style of the place doesn't seem to come into it. If this sort of discrimination was made on the basis of skin colour there would be an outrage, but as it is based on an inherent and unspoken sense of class superiority, it doesn't seem to be an issue with most people.