It helps to get EXPERT, objective advice.
When you talk to people on your side, you're likely to get the "protective of you, we love you" version. There is nothing wrong with that kind of supportive treatment, it's just that people tend to get POLARIZATION from their own people. They are (and should be) on your side. That is wonderful except they can't usually give you a well-rounded perspective at all.
Also, later on when your partner does anything questionable, they are likely to give you the "this always happens" type of view. That's dangerous because people don't come to get advice during the 95% of a relationship when things are going well. Advice, by it's very nature only occurs when there is a problem. Asking people to help you is all well and good, but that means that their perspective of your mate is colored by "that time they did X, Y and Z," not the objective view of the current situation.
I see it often. When people ask their friends and family too often and don't follow their gut, they usually make up their mind to do the MOST EXTREME THING they could do in the situation and then come to an expert to help repair it once it's too late and they acted drastically, spurred on by all this "support" from the people in their lives.
Hope that helps! Also, a few years ago, I wrote this about how to help keep your relationship from getting messed up by this kind of thing: