have boxers. One is 85 lbs and the other is 55 lbs. Though they are the nicest dogs in the world, they hate strangers and anyone who knocks on the door. And boxers of that size, especially the 85 lb one are very intimidating in appearance. I have a boxer. He's about 75 lbs. The word "stranger" is not in his vocabulary. All he sees is a "new friend." He has a VERY intimidating appearance and a bark straight from Cujo hell; but he loves everybody. It's kind of hard to tell strangers what a mean guard dog he is as I hold his collar and his butt wiggles in anticipation of greeting his "new friend" with a sloppy lick.
My male is almost the same way. But if he has never met you before he hates you. After he has met you, or you have been in the house for a few minutes he likes you. But this is only at our house. If he meets you for the first time while we are on a walk, or at a neighbors house he likes you right away.
He knows what is his territory and acts as such. When he is not in his territory, he loves everyone.