My Dad Is a Cuckold. How Can I Express My Displeasure?

I'm so angry. I came home to see my parents this summer and walked in on a horrid sexual scene in the living room I grew up in. To put it simply: Mom has a black lover, he dominates my mom and my dad just sits there and take it. It's like this guy stripped my father of his manhood! I'd like to kick him to the curb myself. But how can I express to my parents how disgusting this is and how offended I am by all of it????