Well, you have to be prepared, and think out the consequences. You should have some leaders who are used to acting disciplined in public protest.

If you choose to shout him down (e.g., for a messy and still-controversial example, http://en.wikipedia.org/wiki/AIDS_Coalition_to_Unleash_Power...) you'd better have a united message and a goal, and media present. And it might still be a bit of a mess. (I had the privilege of attending a lecture on organizing by one of the leaders of this action.)

Other choices are to turn your backs on the speaker, or to walk out en masse.

I'm not sure there was time to prepare for this one, because these revelations are so fresh.

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By the way, you seem pessimistic that this state of affairs can change due to grassroots action. I don't share your pessimism. When people find out the NSA has been scooping up their e-mail and Facebook chats?

We shall see. I hope you're right.

Standing up and turning your back to him, and remaining in that position would have been a classy way to let the general know you disagree.

I wholeheartedly agree, and I made a similar point in another comment.

But no matter what you do, it's totally futile. The NSA knows what you think, and they don't care.