The "slide & delete" option is n/a because iTunes says this TV show was a "Failed download". However, 3.5 GB of my phone space is still being occupied by "Other" (Video).
For some awful reason, the iTunes program on my laptop will not let me right-click delete the TV show out of my TV Shows Library either. I cannot sync my iPhone with new music and organize it because all this space is being taken up. I'm so frustrated I could cry.
I suspect the only way to fix this is to backup the device and then restore it. I have a failed podcast that I too can't remove but in my case the space is negligble.