Some people see all religious institutions in a negative light.
Some Christians see the Catholic Church as having corrupted the religion as a means of monopolizing political and economic dominance in medieval Europe.
Because of that political and economic dominance the Catholic Church was presiding over Europe for over a millennium, so many attribute to the Catholic Church the many violent, repressive, and/or genocidal acts inflicted by Europe on themselves and the world during that time (The Crusades, witch hunts, book burning, inquisition, colonization, new world genocide, African slave trade, etc).
Most recently, their propensity for child molestation, and the covering up of that propensity has contributed as well.