I know that my little guy gets protective too. I know it is best to talk with your vet or seek training for it because it is said to get worse. I think though, sometimes it is just how they feel too....just like we get sometimes and not what to participate in something, share something or just want to be left alone.
I too baby my guy and treat him as if he were an actual human son. He knows he is safe with me and therefore he wants to be my guardian. And I am proud to have a little guy that loves me to much to try to protect his mommy!
Sometimes, if my husband puts his hand on my leg or acts like he is doing something to hurt me (like tickle me or something) and I tell him to stop or make a fuss over it....Mojo gets upset. He will growl and act like it is biting.....at first, we thought he was being protective and now, it is like he is playing with us, just wanting to get into the fun....he doesn't bite my husband, but will growl and go for his hand....it is weird....and hard to explain...it isn't a bite of aggrassion, but a nimble and lick of play...if that makes sense?!
Now, when it comes to a guy coming over.....if he doesn't know the guy (and it is only guys....which, he was never mistreated by a men and I have never been mistreated by a man either, so I don't know where it comes from), but he is like an outdoor guard dog. You know the ones that will bark at anyone driving down the driveway, and not wanting them to get on the porch by the house, etc. He just does NOT like the mail man, the UPS man, etc. I honestly think he feels the need to protect me from them? I do not know why, but I think he thinks he is doing the right thing. He has never biten them, but he lets them know that he would if he had to.
He was also never around kids much.....okay, even though I always took him to school when my daughter went to public school and I picked her up or dropped her off. He even went on field trips with school too. He always went shopping with us, craft fairs, vacations, even to my office when I worked at the university. I think that kids are just loud and they scare him sometimes. Like the summer I had to babysit my neice and nephew (then ages 5 and 7). It was only the 5 year old boy that bothered Mojo! He after all, was a five year old boy...no matter if you told him not to bother Mojo or go into my room (which is Mojo's safe room - crate, etc), he wouldn't listen. He was always running around and being loud or throwing Mojo's blanket and toys....Mojo really hated him.....He did bite him twice that summer, both times with warning before hand. To be honest, I hated to punish him because I knew what he was feeling. BUT since that time, he has not biten my nephew or any other person. Partly, I think, he feels more comfortable around kids (which, they know when they enter my house to follow my rules because of little Mojo being underfoot) and too my nephew learned to behave better!
Too, I wondered at the time, if it was a jealousy thing with kids. The kids that bothered him were always the smaller ones that were more his size, louder and didn't know better and that maybe got more attention? The jealousy with my husband (yes, he is jealous of my husband sometimes) is not an aggressive jealousy....he just wants to be included.....he jumps on my husband and just starts licking him like he hasn't seen him in awhile or gets a toys or nylabone or something and paws at my husband to get his attention away from kissing me to play with him. This again, doesn't happen all the time (maybe it is when he is feeling lonely or like he needs more attention or maybe because I give him more attention then most people do with their pets).
Then, there are times (not all the time) that he will only eat if someone is there by him. There is no reason for aggression towards food because there was never a need to guard his food, even before we got him. I think it is a game to him...as he gets bored and he is a picky eater. For example, if the German Shepard is in, he is more likely to eat his food with her sitting by him looking at him, then just having his food sitting there. OR if you try to get his food, he will growl and try to nip you....we do not encourage this play because that just elevates the thought of his food getting taken away or the need to protect it. Again, this is not everytime he eats and I could count the number of times he has done this on my hands....okay, sometimes he does bite you, but other times he doesn't. I think again, this is a game for him.....he is a picky eater and it is hard to get him to eat and to find food he enjoys to eat (haven't found any food that he really actually enjoys to eat yet).
Okay, it might sound has if he is bored....but BOY is he not bored! I know that no matter how spoiled they are or how many toys, chewies, treats, they get to play with, they can still be bored. He isn't.....he is always played with and when he gets bored with one activity or toy, he gets another one or lets you know he is tired of it. Okay, sometimes he does lay on the desk with me....but that is his choice.
Sorry for the long post, but sometimes I just don't understand why our little furbabies do what they do. I know that I might be wrong in thinking this, but to me, my little guy doesn't appear to have any real aggression issues. My little guy normally does not get nervous or aggressive around strangers even most men....He has a few that he has picked out that he just flat out doesn't like for some reason.....and I am the type of person that believes that dogs sometimes know things about people that we don't. I do not approve of his nips that he has done, but looking back over those situations, I would be nippy too if I had to put up with something like that.