Social Dilemma-Do You Trust Your Pet's Judgement of People?

Today's social dilemma came out of a conversation I was having with one of my neighbors.  She's divorced and she's recently started seeing someone.   They've only been dating for about a month or so, and he's only been over to her house twice.  But both times when he came over, her dog, Pally, barks like crazy at him, and not in a good way.   Now you have to know Pally.  He is the sweetest pup who loves everyone.  When my friend walks him, he can't wait to say hi to everyone in the neighborhood, but for some reason when the new guy comes over Pally growls and barks.  He'll ultimately calm down but according to my friend, is always giving the guy the side eye if you know what I mean.  My friend doesn't know what she should do about this.  I say, pay attention to Pally.  My dog Leo is also a lover.  He loves everyone that walks into the house, but once we had a workman come over and Leo was barking and growling, and I admit, I kept an eye on that guy.  I couldn't figure out why Leo didn't like him.  I asked if he had a dog or pets, thinking Leo must smell the other pets on him, but nope nothing like that.  Never found out why, but I didn't hire that workman again.  I trust Leo's judgement.  I'm not saying there's not exceptions to the rule, but overall, I trust my guy and I think my friend should trust Pally.   What do you think?  Do you trust your pet's judgement?  Should my friend trust Pally?  Let me know what you think on the TRY Facebook page.