You can not use YouTube’s “embedable” code snippet in a WYSIWYG Javascript editor like TinyMCE. That can get very uncomfortable, leading to frequent need to switch back-and-forth between the HTML view and WYSIWYG view. Not user-friendly at all. Fortunately, TinyMCE does have a “plugin” that supports Youtube.

Download: file from the
YouTube Button Issue ticket on SourceForge. Direct Link

Follow the instructions at: