D and the man at walmart

I learn a lot from D every single day, but today I was having a worth-of-blog moment. :) We were going to walmart and D wanted to buy a controller for his computer game. He found the same product with a cheaper price online, and wanted walmart to do a price match. The conversation with the man at the game counter went something like this:
D: I would like to know how much the price is for this controller, please.
Staff: Oh, (let's say) it's $10.
D: I found an item online for $5 (showing the staff person a printed copy of the same item). Can you do a price match?
S: To do a price match, you need to bring the physical ad from our competitor where you found the item.
D: (Very calmly said) I looked online and it said I don't need to bring their advertisement.
S: Oh no actually it's our policy. Without that we can't do a price match.
D: (Even more calmly said) No actually the policy is written here (pointing to a sign in front of that staff person's cash register).
S: It's written there?
D: Yes.
The staff person went out of his counter to read the sign.
S: Oh, ok apparently I didn't know it.
D: (Didn't want to embarrass the staff) Actually I think it's walmart's new policy.
S: Oh, no wonder, I am new here.
S: Hey thank you. Other supervisors always told me that customers need to bring the advertisement for competitors. Now I can tell them "look it's written here."
D: You're welcome.

Oh, my dearest husband. I learned two things today. First, do your research well. Before buying something, D always researches about the product, store policies, return policies, shipping policies, everything. Second, to argue with someone, sometimes you do not need to raise your voice. You do not need to scream. All you need to do is state your argument (or proof?) clearly, with a good intention, and stick with it. :) :)