As a man who was descending to a dark place when I was a teen, I can say this with confidence:

This kind of content, like CP or r*pe-y stuff, even if clearly not real and only a fantasy, feeds these desires, and makes them grow. In time, if you continue to foster it, they will bleed into real life, and then it becomes a real problem. That's why this kind of stuff is scary.

Thankfully, I was able to spot this pattern before it became a problem, that is a dangerous slippery slope