What is it?
Intellectual BS is factual information that has very little value in determining a person's motivation to take action on some perceived "problem" or "opportunity".
Why is it important?
In persuading others it is useful to get some realistic understanding of the other person's type and level of motivation to take action on their problem or opportunity because it will give you better information to formulate your own risk/reward and probability for success for your persuasive endeavor. The basic desire for a solution or reward must be strong enough to keep the person going in the face of resistance that will likely come as they experience the "pain" of investing their time, effort and money/resources required to attain their desired outcome.
Intellectual BS is the type of information someone is generally willing to give anyone - for example the clerk at a gas station - regarding their desires. Intellectual BS may sound like this to you if you are a truck salesperson - "Yes, I need to get a new truck because this one is getting old." Is this really helpful in sizing up the problem with his truck being old and the pain he will experience as he parts with thousands of dollars to get a different one? Could this statement just as easily be heard coming out of this person's mouth by someone conversing with him at a high school football game? There is no valuable information here, but many salespeople will go to their sales manager saying "He's going to buy a newer truck because his truck is getting old." The scary thing is that a lot of sales managers will take this information at face value rather than say "Really? Isn't everyone's truck getting old? What is it about his aging truck that makes him think he needs to replace it now?"
You will need to ask more penetrating questions to get down to the real root of someone's problem - only then can you get a better understanding of what is or could be driving the person to take action. Usually real motivations will have an emotional element to them because emotions are really at the root of any motivation...Intellectual BS is a form of smoke-screen to protect one from emotional pain or vulnerability. If you genuinely care about the other person you will not abuse any access they allow you.