Yeah, I have had people shout "No spoilers!" at me for the example I quoted, and I agree it's pretty silly. Where exactly the line is, I'm not sure--is talking about a specific minor scene that isn't plot important a spoiler? Well, kind of, but not on the same lines as giving away THE twist, or someone's death, either.
I have a couple seriously spoiler paranoid friends, which has given me an increasing aggravation for people who overreact, though.