Video Blocker allows you to hide videos from channels that you don't like. You can specify these channels by right-clicking on a link to a video on YouTube or by adding them manually via the options page. You can also hide videos from multiple channels at once, by using a wildcard. For more information on how to do this exactly, please visit the help section after installing this extension.
This is the Firefox version of the 'Video Blocker extension' for Google Chrome. Some features might not yet work as smooth as you'd like, so please report any problems to me if you find any!
Good luck and happy video blocking!