"To challenge those stereotypes" means to question or dispute the commonly held beliefs or generalizations about a certain group of people or things to break down those biases or preconceived notions. Full definition
This is not a film which challenges the stereotypes of teen coming of age movies. (flicks.co.nz)
No surprise, then, that hundreds of dads are now blogging about parenting — and challenging stereotypes about fathers. (npr.org)
His aim is to empower and encourage young people to discuss and look after their mental wellbeing and simultaneously challenge the stereotypes and stigma associated with it. (qaeducation.co.uk)