Because of the inclusion of Freedom's Watch's website address:
What a shame they won't make an exception to their policy for these ads because they really are quite lovely. See for yourself:NBC has nixed holiday advertisements meant to thank troops for serving overseas in opposition to the inclusion of a non-profit's Web address
The ads, paid for by the non-profit Freedom's Watch, are a simple thank you, the group says, with people shown paying gratitude to members of the military and the final frame showing the group's Web address, www.freedomswatch.org.
[...]
NBC is refusing to air the ads as long as the address is included, according to an e-mail exchange between NBC and the group, which Freedom's Watch provided to FOX News.
"Per my previous email, the www.freedomswatch.org website will have to be redacted from the commercials for approval. This comes from Alan Wurtzel and Rick Cotton," according to one of the notes.
Wurtzel is president of research at NBC. Rick Cotton is general counsel for NBC Universal.
