Forum:Patronus article problems

The Patronus Charm article states that J.K. Rowling was quoted saying that Snape was the only Death Eater that can conjure a Patronus. It is uncited and I, personally, haven't been able to find anywhere where Rowling said this. If it can't be properly cited, it shouldn't appear there, of course. It doesn't seem to make any sense. Umbridge, one of the most despicable people in the Potter universe conjures one and Bellatrix doesn't seem like she'd have too many problems "thinking happy thoughts." Furthermore, the Death Eaters would need to use the Patronus Charms to control the Dementors.