If an agent takes offense to that... oh well!

In Washington state, it can be considered a criminal offense to record a conversation without someone's permission. 

I guess I would start by copious amounts of baking soda in offensive areas. 

Yep, you have a sneaky Realtor there, lower the hammer and get them off the streets.The best defense is a good offense, I'd say that if send any threat of legal action in writing, they are dosing themselves with gas before walking into the fire.I agree with Dion, this is probably not their first dance.

I, as well as my co-agents, find it a little offensive when someone asks to do such--it puts us in an awkward situation.

Not trying to be offensive, but it seems like a lot of folks are making comments on the historic market from markets with almost no historic houses. 

(boring is the wrong word but i hope you know what i mean).more on the landscaping...i'd have any bushes or plants in front line up to be the same height.  

Ben,that is a criminal offense on both his and your part.You are attempting to defraud the government of tax dollars and you will be prosecuted when it is discovered eventually.Tell them no and leave it at that.

My front line manager and co-workers know.

its no different than me teaching someone how to trade for a living, no offense but you make it sound like people in general are cynical in nature