I've never had someone threaten to damage my gear but I'd probably just calmly inform them that my insurance company would cover it, and then sue her to recover their costs. and that I would be sueing her for my lost income for the time I'm without equipment and then the bar will ban her permanently and she'll probably be arrested. Then just smile and say "go for it, I'd love to have you buy me a new mixer".
I get a few pushy people though and I don't know why they think it's a great idea to request songs that are nowhere near the genre being played. My Friday and Saturday night spot is what could best be described as a nerd bar, they have a library of board games, RPG books and card games; Xbox and PS3 stations; video game themed food and drinks, etc. I play a wide variety of music including, industrial, nerdcore, VGM, EBM, belly dance music, irish trad, house, trance, electro, 80's and dubstep. What I don't play is hiphop/rap, that's the music that the people who beat up our patrons in school listen to and they hate it with a passion and the owners can't stand it either. I get people who are obviously not a card-carrying geek that come up and ask for lil wayne or nikki minaj and then act like they've been insulted when I tell them we're not a hiphop club. If they get pushy about it I've got a rotating list of responses that I use.
What do you think the DJ at the hiphop club you usually go to would say to me if I went up and told him his music sucks and that he needs to play something better like country or finnish goth metal?
The bar pays me X, if you want to pay me more than that I'll let you pick out the music.
The owner told me that if I play any more lil wayne, etc she's going to drown me in the fryer while shoving a rabid weasel in my pants.
This is my spare laptop, I don't have any good music on it.
Buy me a drink and I'll try and fit it in, I'd like a pitcher of scotch.
I don't have a hiphop license.
That girl over there said she'd sleep with me if I don't play any (artist name here).
Only if you can tell me, without using the internet...
-How many hit dice a beholder has.
-Who played the 10th doctor.
-The formula for calculating the volume of a sphere.
-The name of the 3rd boss in the plague wing of icecrown citadel.