We have included a media filter in our public beta, this will let you control what media stream you connect to, allowing you to whitelist or blacklist any media stream.
You can enable or disable the filter in Preferences, Audio and Video.
If enabled when a stream starts to try playing you will get a window on your screen that lets you choose what you want to do.
Your choices are:
You can access the media list through the Phoenix menu.
The media List allows you to add or remove URLs from either the whitelist or the blacklist. Note that you can use the Add button and manually add a URL.