"They laughed at (insert name of paradigm shifting thinker here)." Are often the words that come out of the mouth of some the crank, scam artist or con man. What they are trying to do is get you to think of them in the same light as someone who struggled to change how the world things. The con man wants to borrow/steal some of the authority of the great thinkers.
The difference between the crank and say Thomas Edison is that the crank comes up with his idea and tries to convince the world he is right because there is some great conspiracy holding him back. The scientist works many years refining his hypothesis, tries to falsify his claims, presents those claims to a group of his peers for review, and if his claims are rejected he returns to the drawing board to figure out what he has done wrong.
The great geniuses do not blame others for being closed minded when their findings cannot be reproduced. They go back and comb through their data until they find where it was they made their mistakes. They know that if experimenter after experimenter fail to reach the same conclusion that they did, it was not because someone is trying to hold back there ideas, it's because they made an error in calculations.
It is true that every scientist wants to be the next Einstein, Newton or Hawkings, but they are not willing to trash their reputation to block a legitimate break through. What good does it do them to halt progress. If a hypothesis is shown to be correct, it opens a whole new world of possibilities. It not only brings to light unknown information, but it also brings in more money to fund research into that newly discovered field. It opens up new opportunities for a scientist to make a name for themselves.
The crank does not seek out the opinion of his fellow scientist. No he takes his hypothesis straight to the public. He claims that he is just on the verge of a big breakthrough and that if he could just raise enough money he will be able to complete his research. He might even show a prototype of what it is he is working on. But don't be fooled, often times he is just misapplying science that is well understood.
There are no perpetual motion machines, there is no free energy devices, there are no pills that you can drop in your gas tank to get you better fuel mileage. These are all scam designed to line the pockets of someone looking for a quick buck. They fly in the face of hundreds of years of accepted and proven science. We know these things don't work because every time they have been put to the text they have failed. The same with Homeopathy, Numerology, Chiropactie or any other New Age/Ancient wisdom claims.
Science has yet to find the answers to every question ever asked. But every time it has manged to come with the answers we discover that the old magical thinking was wrong. Things are not governed by some magical force. Everything in the Universe follows the same set of physical laws. And if we ever run up against some object that falls outside those physical laws, it will be science that finds the answer, not a crank.