The bashing of M. Night comes from his previous films being very pretentious and trying to hard to be so mind-blowing they rarely lived up to their hype. Add to that, "Signs" has the most illogical backstory that most sensible people can't just overlook -- Why would a race of aliens who are afraid of water invade a planet whose surface is 1/3rd water?! -- And this is where a lot of the anti-Shamylan sentiment comes from.
General_Maxiums often makes a lot of sarcastic comments in his/her posts, but most are tired and cliched