Shipping does play a part in the Musketeers fandom behavior. They're angry at how the previous love interest was treated on the show, but that doesn't excuse the treatment of the new love interest.

And then there's the issue which as a white person I'm not sure I can adequately speak to. Suffice it to say the new love interest is a woman of color and the previous one is white. And the man is white. And all I can say is I have definitely seen a pattern when it comes to mixed race pairs on tv shows. Especially when it's a woman of color and a white man.

Besides that there are a couple of other women on the show who have been spoken of terribly and I honestly have no clue what that's about other than internalized misogyny.