In Syndrome's defence, the displacement of feudalism wasn't always a peaceful affair either but it's a change we can all agree was necessary. Violence doesn't change its inherent nature just because one puts a respectable face on it, the hereditary category of 'hero' can only exist at all in an otherwise democratic society because of the implied threat of 'I'm going to use my magical powers to take down anyone who opposes my interests', which is unacceptable because they don't have a legitimate claim to the use of force stemming from democratic consent of the people in the way say the military of a modern Western country does.
We see this at the start of the film where Mr Incredible and his friend get tangled up in a rescue operation in a burning building despite having been pretty firmly rejected by baseline humans they're attempting to help, if I remember right one of them literally gets frozen alive by Mr Incredible's friend as they escape which is rather violent. We also see it when he throws his insufferable boss through several walls in a fit of anger, which is a display of his ingrained violent nature and lack of control over his superhuman powers which presents a threat to innocent bystanders. It's might-makes-right with a veneer of heroic respectability over the top, their true nature is very different from the nature they present to the public.
Either that or I'm reading way too much into a film that's mostly aimed at kids!