In all likelihood, the false positives suggested by the OP and others in this discussion are unlikely to trigger any such NSA attention.
Coming from a data science background, I suspect they are transcribing and indexing all conversations as best as is possible with their elite voice recognition technology. Once it's in ASCII stored in a database, they can datamine the conversations of known radicals and jihadists. The algorithms that are generated don't so much emphasize specific keywords, but they generate a scoring system across a bunch of conversations by known haters-of-American-Freedom.
With filters in hand, they can look at who talked to the known villains and score them and run down the trails of phone calls, emails, text messages, and internet chats to see who else might be a solid villain candidate. Even just monitoring internet traffic to known jihadist websites can likely get the filters applied to a person's communications to see if they might be a person-of-interest.
Keywords will come into play AFTER an attack like the Garland Draw Mohammed contest. The NSA is right now filtering recent past conversations among suspected jihadists looking for relevant keywords such as 'Garland', 'American Freedom Defense Institute', 'Pamela Geller', and 'Elton Simpson'. Any conversation leading up to the attack including those keywords would absolutely put someone on a watchlist. And everyone who that person is talking to would be suspect as well.
Bottom line is, these tools are being used retroactively to bolster detective work. Talking about bombs and the President's name doesn't do anything because there are a thousand-million conversations using those words everyday.