Pink recently caused a controversy when she cancelled a concert at the last minute, which caused some fans to get extremely angry and write a lot of hateful messages towards her. 
Kelly Clarkson during a photoshoot
The cancellation was allegedly due to an illness which Pink had no control over, but angry fans hit out against her and said that she didn't 'care' about her international fans and that she was 'faking' the illness because she just didn't feel like performing. Although Pink herself responded to all the angry fan comments by writing a massive letter to her fans, it didn't make the headlines until other celebrities started pitching in and giving their opinions.
Kelly Clarkson was one such celebrity, and she wrote a message to Pink on her Whosay account saying, "How dare you only work 364 days this year. I can't believe you got sick. That never happens to anyone ....ever. You're so lazy #nameonepersonthathasherschedule,singswhileflying,andisamom ....seriously people. Tired of seeing everyone giving her crap. We're all human. Relax." Pink's message to her fans, on the other hand, read, "I am a human being, therefore I am able to catch illness. It is beyond my control- and I can't apologize for that. And you know what I've been performing through the last week? ROTA virus. Look it up. I challenge any one of you to do what I do while sick with that. You couldn't do it."
Kelly Clarkson defends Pink against angry fans
Pink is currently on her 'Truth About Love' tour, and the concert she cancelled was in England. She will finish the European leg of the tour later this month, and then go to Australia in June.
A P!nk and Kelly Clarkson song mashup
