As I've already partly mentioned, I travel frequently through the top 3 busiest airports in the UK and have never encountered the alleged unpleasant security staff. Sullen on occasions, yes, but never nasty, so I'm slightly puzzled about this debate. I've experienced worse problems with the security people at Schiphol and the passport checking people in the UK than any of the security bods in the UK airports.
I would also support the accusation that it is often stupid people who delay the queues by not doing as requested and separating liquids, removing outer coats, belts, removing laptops from bags etc before their turn. The number of times I've been held up by idiots carrying more than the 100ml and arguing the toss, or people fussing with a laptop defies belief
However, it's the 'frequent fliers' with attitude I despise the most...I'm sure we've all come across them at one point or another!