You might want to avoid pairing "Obama" with "bullets" in the same sentence. Even though any sensible reader will understand the context, if you give the secret service enough rope, they won't defer to common sense, not when a statement can be stretched to a possible threat. Your comment will bomb with them, and they will go nuclear over your choice of words. It's just nice to be careful because a couple of careless key words can invite unwanted attention and poison the whole discussion.
I'm pretty in tune with implied threats, and the poster's comment didn't give me any impression of that at all. "Sweating bullets" is a longstanding phrase well understood to have ZERO to do with violence.