As posted in the same question from before:
At the top of the agreement, it says, "it's required for a Realtor to have a signed document before representing them" (not verbatim).
First, we need to have an agreement in place to actually be able to perform the duties that look out for your best interest. We have a fiduciary responsibility (this is the same responsibility that attorneys have) to look out for your interest.
Secondly, if you are visiting listed homes, homes that are listed with agents, then they have ALREADY agreed to pay (usually) the Buyer's Broker something. Since that agreement came first, it rules the day (in the event that a Seller decided on this argument).
Lastly, let's be real. Who pays the commission is debatable. I won't be popular for this answer, but if you really think about it, who really pays. The buyer is either paying a little bit more for the home, due to the commission (even in the event of a FSBO, the seller often prices their home similiarly to listed homes thus, most buyers pay a commission... to the owner) OR the seller is taking less than he could (assuming you thought the home was worth what you are paying) have taken.
That's the pessimisstic engineer's view of things. Bottomline, your agent is there to look out for you and should advise you on when you might be in a situation to pay an extra commission (FSBO scenario).