Dick Knights Mumm
Take me Home Falmer Road
Its the snobbery from the ale drinkers / bores that fuels the divide, tbh. The condescending "ah bless, he drinks lager. What a philistine", as opposed to simply accepting that not everybody has the same taste in beer. Some people LIKE stella / Amstel / Heineken / Whatever.
The old Hobogblin advert - "What's the matter lager boy? Scared you might taste something?" sums up the whole sneering attitude perfectly. You'd see some prick in Docs and black jeans, with a too-small T-shirt, emblazened with that, stretched over his fat real-ale gut, and just think "yep. You're great fella. I'm so missing out, on being as COOL and discerning as you".
Do these people really exist in this decade ? More common lighter real ales, better lagers, generally better kept beer have all blurred the lines. I just do not recognise the type of person you describe.