Dolores is played by an attractive, intelligent, and outspoken young woman. Some men seem to have a lot of trouble with these things.
Actors often get a lot of hassle and their characters a lot of hate. Sarah Wayne Callies, Lori from The Walking Dead, and more recently Brie Larsen who plays Captain Marvel in the MCU. Some men, a lot of men I suspect, don't appear to like strong women.
Misogyny, that's what I think the reason is.