Because sadly there are some whose identities and self worth are defined by a belief in their superiority over the masses. And in this case there are some who make themselves feel superior to the average or typical WDW visitor by believing that only they understand and recognize the true purpose and mission of Walt Disney, and that the average folks are clueless and don't get it. To them, any opinion that does not fall in line with their particular view must be ridiculed and dismissed because it is inferior, and because to acknowledge that any other opinion is also legitimate, would be an admission on their part that they are no more superior or special than everyone else on this planet. Likewise, there are some whose self-worth and identities are wrapped in being the ultimate Disney fan - and for them, Disney can do no wrong and any criticism must be squelched.
By and large, most people probably recognize that for something like what people like or do not like at a vacation destination and resort the size of WDW, and with the diversity of attractions, entertainment, and customer base of WDW, there will necessarily be a wide range of opinions -- what one enjoys for entertainment, leisure, vacation, etc. is of course inherently subjective. As such, most people will probably respect the diversity of views even if they don't share them. But this is a Disney World board, so you're of course going to attract all types, including the superiority complex types and the Disney can do no wrong types who have no tolerance for anything that doesn't fit into their narrow view, and because the latter groups have so much more of themselves invested in and dependent on these issues - their very opinion of themselves - they tend to be over represented on these boards and in the post counts.
My humble suggestion is to consider taking what you like (all the great information and diverse viewpoints shared by so many here) and leave or ignore the rest (the silly attacks, condescension, and overwrought reactions).