I have a disgusting secret fetish
What is the fetish?
I like to watch a rape scene in porn videos
If you have an unusual fetish then you should keep it in the realm of fantasy.  If you feel like you actually want to act on this, you might want to seek mental help. Actually committing a rape in real life is obviously not okay.
Why is it a problem if I like rape? It's okay if I rape girls.
Simulated rape in porn videos is just a performance, it is never okay for anyone to act this way in reality.  If you have a desire to commit such an act, you should talk to a therapist to help get over it.  But as long as you recognize that this is just fantasy, then you can enjoy it in a fictional format.