1) Get rid of all words like "rationalism", "reasonablness", "empiricism", "telology", or any / most scientific and philiophical terminology. There is a good chance everyone will be talking past one another. This must be demanded, or you will be in an uphill battle.
Speak as plainly and colloquially as possible. Most scientific jargon in this discussion will be empty symbols (as they will not be effectively communicated inter-subjectively) or simple appeals to authority.
2) Simply discuss how things work, and what can and can not be said about such things. Talk of the nature of how things are manipulated, and why that is the case, etc etc.
If you are satisfied with the results be gracious and let your sparring partner name what he wants to call these conclusions. If he wants to call them "the emperor of china", "socialism", "anarcho capitalism", "empiricism", so be it - it does't matter.
3) Leave all ethics, aesthetics, and political theories out of it. Do not enter them into the conversation, and do not allow them to be thrown into the conversation. There is no need for them, and they will only confuse matters. Be militant about not letting such trivia slip into the conversation.
4) Do not speculate on the future, and take all of history off the table to be discussed. This is useless pondering.
"As in a kaleidoscope, the constellation of forces operating in the system as a whole is ever changing." - Ludwig Lachmann
"When A Man Dies A World Goes Out of Existence" - GLS Shackle
Good advice. Could you give an example for #2?
It could be something as simple as "I see, I want" which could lead into actions and common scenarios that deal with scarcity - supply and demand, STV, etc etc
The minute someone gets philisophical with the conversations about asking what "I" means (for example) - simply ask him if he has no conception as to what "I" is (no picture, no custom, no general impression / expectation, etc) ; if he says "no" - simply say "thanks for the conversation" and walk away.
One of the hopes is once you get rid of all bogus scientific and philisophical presuppositions and pretentions language should open up to a more "good faith" (or better put, a more utilizable currency) approach of definitions. People may become less gaurded - this will hopefull hold even more true when you take politics off the table.
Keeping history off the table would tick off most empiricists.