This reminds me of religion based talk. Both sides do their best to defend their opinion, yet there's no agreement. This kind of discussions really lead to nothing. Those who don't like hybrids, won't start liking them because of whatever contrary opinion they read which supports them, and vice versa.
To those who use hybrids, like someone already said, isn't it better just to ask if they can use them when they enter a room? If they don't allow it, then just use a different car or find a diferent room. If the ones with hybrids insist on using them, just boot them. People even quite often kick others who aren't of the same country, so kicking because of hybrids shouldn't be much of a hassle either.
Regarding those with barely noticeable hybrids who get in "undercover", just look at them closer, either they'll have something physical diferent about them, or I'm sure you can notice something diferent about their performance, as some stated they did notice already.