Ok, I was just wondering what exactly was inappropriate and how he was reacting. If you are unsure, as you say you are not qualified, if you don't feel he is dangerous (as long as you exercise some common sense), then do as Randy and Al said and get to know him, hang out w/him, earn his respect.

You're trying to rehome him? It's hard to rehome a dog that you don't have the skills or experience to thoroughly understand/test/evaluate. Is someone qualified going to be helping you in this process? I did not have time to read you link; sorry if this was answered.

I am not being critical; I'm just saying this as something to think about; you don't want this dog to end up in someone's home who cannot properly deal with him. Just wondering about the logistics and next steps.

Two year old males can be major butt heads....LOL

If you fostering with the idea of rehoming I would forget and protection training and work on the things that will help him fit into a forever family.

Like Al said, first thing is the bond. With new dogs we play a lot of ball with them and incorporate commands. You want me throw the ball? No problem, give me a sit or a platz. Even with a dog with no training, you can pretty much lure them into position with hand motions.

Dog learns real quick....hmmm good things come from these crazy people if I play their silly game...

Same with food, sit and wait for the release. Initially I often look like a traffic cop with my hand out in front of their face like a stop sign, but again they learn.

Personally I would try and avoid situations at first if at all possible where he alerts at the end of leash until I have a bond. Once that is established, I would give a calm leash correction, and continue the walk.

It's hard to give much advice without seeing the behavior. It could just be buttheadness, it could be training, it could be temperament. But since he ended up in a rescue at that age I kind of lean towards clueless owners that let him get away with stuff.