Hundreds of people scorned Watson, a UN ambassador for gender equality, noting the meme posted in remembrance was simply "furthering her own political agenda".
Rickman, a staunch believer in parity between men and women, died on Thursday from cancer.
"There's nothing wrong with a man being a feminist - I think it's to our mutual advantage," he had told ABC in an interview in March 2015.
Upon hearing of his death, Watson posted a string of tributes on social media, including one that carried the quote.
The quote received overwhelming positivity on Twitter, garnering over 66,000 re-tweets, but failed to pass muster with some that who took exception at its content.
Undeterred, Watson continued publishing posts to express her sadness at Rickman's passing, including one from another the actor and director's frequent co-stars, Emma Thompson.
Thompson, who worked closely with him for decades, said the 69-year-old had been "the ultimate ally. In life, art and politics."
Watson also included a tribute from Sir Ian McKellen, who said of Rickman that he "put liberal philanthropy at the hear of his life".