I wouldn't use the word 'charlatan' as leniently. Without commenting on the validity of their work, the 'mainstream opinion' about them is most certainly negative. Yet instead of pivoting elsewhere, they stick by their convictions. They might be right or wrong on their opinions, but they are hardly doing it to win any favours. And it's certainly not wrong to stand by something you believe even if the mainstream discredits you; time will tell who was right.