Einstein actually faced fairly stiff opposition to his ideas amongst physicists, especially his ideas about special relativity early in his career, A lot of it was driven by the fact he was an outsider to the physics community at the time. [1]

>This world is a strange madhouse. Currently, every coachman and every waiter is debating whether relativity theory is correct. Belief in this matter depends on political party affiliation." Thus begins a letter by Albert Einstein to his one time close collaborator, mathematician Marcel Grossmann. It was written on 12 September 1920, just some three weeks after Berlin’s Philharmonic Hall had hosted a rambunctious rally at which Einstein had been denounced as a fraud and scientific philistine.

Another good example of a revolutionary innovative thinker of the time being branded a fraud and a charlatan by mainstream voices is Georg Cantor, who was so badly treated he suffered mental illness for much of the rest of his life because of how completely his theories had been rejected. [2]

[1] https://arxiv.org/pdf/1111.2181

[2] https://infinityplusonemath.wordpress.com/2017/02/11/no-one-...