I simply didn't react quickly enough. I saw him set the bevnap he was already
holding down on the speaker, and then immediately dump it out - one quick
motion, basically as he agreed to give up his glass.
The yelling match did go on too long, that's for sure - probably about 45
seconds to a minute, at which point I simply walked away.
Edit: The speaker is about the height of my sternum, right next to the stage -
it IS used as a table for empty glasses sometimes, when the barbacks and
myself get in the weeds (we usually clear it off before anything else, for
exactly this reason, so nothing happens to the speaker), but in general, there
isn't anything on it.