Nikkie was undoubtedly upset at J.K. Rowling because she said a lot of genuinely transphobic things lately, and although that statement perhaps wasn't overtly so, it was condescending (trans people are just confused and don't know what they want). Seriously, there are not "a lot" of trans people who regret having sex reassignment surgery. It's part of a larger context that is offensive, in part because it isn’t actually “the truth.”