We listen with our ears but hear with our emotions. Every sense we possess runs through the lens of our emotions and that lens can pretty easily warp our feelings.
Take for example spit. Imagine spitting saliva into a cup then drinking it again. Gross, right? Logically we know that emotion is absurd. The saliva was just fine a millisecond ago while in your mouth. As soon as it is outside we are repulsed. That's our emotions clouding our logic.
If we are told a piece of audio equipment has been getting bad reviews or the opposite, we tend to cloud our judgment with these pre-biases. But, we don't have to.
Understanding the power of emotional bias is often enough to counter it. I know that in my own case if someone asks me to audition a piece of equipment or a new circuit, it's a lot easier to cut through the emotional baggage if I don't know what the opinions are. But, even if I do, understanding pre-bias is enough to cut through the lens and get to the truth.
I am sure you already know this, but it bears repeating from time to time.
Your first reaction can be a powerful tool. If it's been preconditioned, ignore it. If it's fresh, pay close attention.