This might have been true in the early 1960s, but during the past four decades Hollywood has usually followed an unspoken, self-imposed rule: "Thou shalt not cast a black man or woman as the evil character who remains unrepentant and unredeemed."
From Bill Cosby to Will Smith, black actors who typically play "good guy" roles have been impossible to miss, not impossible to see.
Sorry, it is absolutely untrue. Have blacks gotten better roles in Hollywood? Sure they have. Sidney Poitier had good roles, Morgan Freeman gets good roles, Eddie Murphy and Will Smith get good roles. These are the exceptions to the rule.
Star power aside, the AVERAGE black in TV and films is portrayed as a thug, doper, or other criminal. The AVERAGE black American doesn't see themselves as Morgan Freeman, Will Smith, or Eddie Murphy. Unfortunately, they see themselves as they are portrayed by the myriad unknown black actors playing thugs, dopers and/or other criminals.
And, the likes of Bill Cosby and other prominent blacks who try to encourage black Americans to "get with the program" are castigated by the race baiters as "Oreos" or "house slaves".