Here’s how to block someone on YouTube.
1. Log into your YouTube account. If you’ve already signed in to your corresponding Google profile, you won’t have to sign in again.
2. Go to the profile of the offending person by clicking his or her name wherever it appears in YouTube. This might be on a comment on your video or channel. You can also run a search for his or her name at the top.
3. Click About from the list of options under their name.
4. Hit the flag icon at the top.
4. Select Block User.
5. Confirm by hitting submit on the next screen.
When you block someone on YouTube, they won’t be able to comment on your videos or channel, and will be barred from sending you private messages too.