Dash isn't "a petulant child", he's the voice of the movie. He's voicing the same thoughts that Bob has hidden, in an attempt to "fit in;" to "be normal." Dash's inability to cope with the mixed message of "do your best" while simultaneously being told, "don't be better than other people, though" is at the heart of the movie. When Syndrome expresses his desire, along with supervillian chortling, to make that bleak situation a reality for everyone, the ridiculousness and untenability of the scenario are highlighted.
At the end of the day, it also doesn't matter which character voiced the thought; the plot itself presents that as the main human drama conflict to be resolved, a bigger conflict in many ways than the more surface conflict with Syndrome and his organization; the real conflict is the ideology represented by Dash (and Bob) vs. that of Syndrome.
At the end, the superheroes are justified; they're allowed to come out of hiding and resume their superheroing duties, because victory over the tyranny of political correctness causing them to hide or not use their powers for fear of being better than the average person is assured.
Obsessing with who said a given line is completely beside the point.
You're wrong. You're just adding stuff into the movie that isn't there, oversimplifying various aspects of the movie, and blatantly forgetting very important parts of the movie.
Alright, here are a few basic facts about the movie.
Dash is just an exaggerated version of the typical boy who hates getting told that he can't do something by his parents. He is basically a bit selfish and very bratty and rebellious. He is certainly immature. He grows a lot by the end of the movie, though, which is indeed the main point.
Bob is an exaggerated version of the typical man going through a mid-life crisis, pining for the adventure and romance of his younger days, letting nostalgia obscure many of the problems. The fact that his wife gets the mistaken impression he is having an affair is perhaps the clearest sign of the fact they are making this parallel...
Syndrome, as he was when he was just Mr. Incredible's fanboy, was just like Dash. He was a bratty, spoiled, and selfish kid. His flaw was that he just didn't grow up. He continued to be bratty and selfish his entire life. This is probably why the people at Pixar gave him the height and appearance of a child when he is grown up.
Syndrome's threat has absolutely nothing to do with making everyone endure some kind of situation of both being "special" and being told to :not be better than other people". I honestly have no idea where you got that from. You seem to be assuming somehow that Syndrome is some kind of parallel for "political correctness" and he stands opposite of the desires that Dash and Bob have early in the movie, but that is completely false. Syndrome is the very incarnation of the desires and ideology that drives Dash to want to be "special" and makes Bob want to relive his youth.
Honestly, I don't think the idea of "political correctness" is even a significant factor in this movie. The Incredibles don't stay under the radar because it is "politically incorrect", they do so because they want to have a normal family. As is shown in the later parts of the film, the Incredibles and the ice-powered guy really don't have any kind of real fear of using their powers when it is necessary to help others. The real event that brought an end to Mr. Incredible's days as a superhero wasn't the lawsuit against him, it was his wedding. The last time he ever wore his mask as Mr. Incredible prior to the main action of the movie was the moment he took it off after putting on his wedding tuxedo. Mr. Incredible didn't just hold his insurance job to keep a low profile, he did so because it was a way of earning a living to support his family. The burdens of married life and raising a family is really what kept him from being a superhero, not anything else.
Anyways, to finally get around to my main point (and I really am no longer addressing Hobo here)... The idea of "specialness" you see in Dash and Syndrome's quotes is basically those two's desires to be, well, worshipped because they perceive themselves as special. I don't think it really even has anything to do with the actual fact of their specialness. The story of
The Incredibles is a big metaphor for the trials of a
normal family, of any family, not necessarily a family that has a potential olympic athlete for a son. Dash and the young Syndrome are both parallels for the average kid who dreams of being just like some role model and believes that they are uniquely awesome simply because they
are uniquely special to their own parents. If you want to get psychoanalytical about it, it could be said that their desire for other people to "recognize their specialness" is nothing more than a foolish desire for everyone to love them unconditionally the same way their parents do. In Syndrome's case, this became such an obsession that he enacted a grand insane scheme to transform himself into the world's only superhero and savior, live as such until he grows old, and then make sure that no one ever becomes as "special" as him ever afterwards.
As one final note, people should keep in mind that Syndrome really is a pathetic little man. For all his desire to be seen as a superhero, he only wants to do so when he has no competition for the limelight and when it is 100% safe for him. If he really wanted, he could have started acting like a hero and used his technology to stop bank robberies at any time.