Suppose a scientist holds a minority opinion. There’s a trend in journalism to call him a denier if you think he’s wrong, a skeptic if you don’t care, and a maverick if you think he may be right. If this had been the norm in Einstein’s day, he might have been called a Newton-denier.
“Denier” is an ugly word. It implies that someone has no rational basis for his beliefs. He’s either an apologist for evil, as in a Holocaust denier, or mentally disturbed, as in someone in psychological denial. The term “denier” is inflammatory and has no place in scientific discussion.