unfortunately quite a few of them. like mrwizard pointed out, people like this are probably those same folks who put up the following LFMs:
chronoscope normal: lvl range 20-20 "loot run need healer"
<insert raid name here>: "no noobs, need guide"
waterworks: "need tank" <--my personal favorite, tank those ankle-biters!
the general population is ignorant, sees the raid completed a specific way and refuses to derive from that method. There is also a lot of misconceptions out there, like "don't move in hound or youll start beholder timers". must have X hitpoints or you cannot do epic content, period. must be lvl 18+ to do this and this raid.
It sucks, but this is why we are in good guilds with like-minded players. Pugging simply serves to remind us how blessed we are to be sheltered by fellow competent players.