You don't. If you want to watch a video, they will want to verify your age and an agreement that you have read their acceptable use policies.
How Do You Watch A Sexual Video On Youtube Without Having To Sign Up?
I don't know I am already signed up
Why go to youtube? Just go to rawtube if it's sexual things that you're looking for.. And no lol I don't go there. My boyfriend told me about it. :D