So...leaving your other points aside, you do realize that this was said by a supervillain, right? And not just a supervillain, but a specifically "angry about not being instantly beloved by senpai~~" supervillain. A supervillain who had built his whole life around trying to "prove" that Mr. Incredible was ACTUALLY the REAL jerk because he refused to accept the supervillain-kiddo's UNDYING LOVE AND PRAISE.
Like...this is a dude who was literally stalking someone, got super ultra told off for it. Then instead of, y'know, learning to respect others' boundaries and accept that just because you feel something for someone does not in any way oblige them to feel anything for you, he instead bent his (significant!) genius to proving that Mr. Incredible SHOULD have loved him just as much as he loved Mr. Incredible.
That line is, quite literally, exactly equivalent to an internet Nice Guy becoming so upset about a pretty woman not reciprocating his feelings, that he spends his whole life finding a way to make everyone beautiful solely to prove that beauty is unimportant. It's honestly mind-boggling how many people think this is a Vital Philosophical Truth when it's just an angry man-child vapidly insisting that the world SHOULD revolve around him.
(It also doesn't work at all if you even slightly think about it. "If every food is delicious, then no food is delicious." "If every book is good, then no books are good." "If every outfit you wear is comfortable and stylish, then no outfit you wear is comfortable and stylish." It's just utter nonsense that SOUNDS profound. Which is the whole point of Syndrome as a character; he's vain, completely self-absorbed, and so shallow that a walk through the ocean of his soul wouldn't get your feet wet.)