I am one of the defenders of Singer's movies here but this is indefensible (yeah, innocent until proven guilty blah blah but c'mon, guy holds parties for minors/barely legals and dresses up like a priest). People need to keep talking about it as long as accusations keep arising because if he keeps going unchecked, several kids are still at risk. Including young actors trying out for X-Men movies involving him.
And as somebody said, Chastain has to be more in the know than any of us being a Hollywood person and all. She was one of the few actresses to completely avoid Harvey Weinstein because she was aware of his behaviour pretty early on in her career. So she knows what's up.