Boss obsessed with licking/sniffing other dogs genitalia

I have noticed that Boss has a big problem with obsessivly sniffing and licking other dogs genitalia, especially other males. He has never mounted another dog or human before. But I havent had him over to peoples houses if they have dogs because he will follow them around and do his sniff and lick. When I bring him over to my mums house, my mums male dog Tazz(a very large Border Collie) can be quite territorial, but lets Boss walk around abit, and then as soon as Boss goes to Tazz he shoves his nose in his bits and then gets a loud growl and a warning bite from Tazz. I am wondering if there is a way to get him to stop this behaviour? At some point I might be needing to be living with my mum for abit during college and if he cant stop his obsession he will have to be in the outdoor kennel, he isnt a dog who will fight but I am more concerned that Tazz would be attacking Boss and harming him, and being in the kennel all the time isnt a way to live.

How is he with his commands?

I don't know if it would be possible but perhaps distracting him before he gets too obsessive (he must still be allowed to say hello to other dogs) but then ask him to return to you and sit. Then reward with either a treat or his favourite toy.

Its not something I have encountered before so not 100% sure. Is he neutered? That could help a lot if it isn't already and if you aren't against the idea.

My young boy has just started to realise that he is a boy and tries to mount other dogs but I find that I then say his name and get him to come sit by me, treat him and then he doesnt do it again. We shall we see what happens as he gets older and more persistent though. Then hopefully I'll be able to convince the bf to have him neutered =D

He is only really good for commands if on a leash, when he is off the leash he gets very distracted and wont listen to well, has gotten better but still not 100%. He got neutered last June, when he was 2 years old, a couple months after I adopted him. He does get to do his first hello, but then continues to go and sniff and bother, etc. He does not play with dogs or toys so I am not sure if this is his way of interacting instead of if he was to play.

Have you practised doing commands on leash with distractions and then gradually adding distractions off leash in a safe environment? He should ideally respond regardless of whether he's on leash or not (the dream world I know!)

You don't know someone with a friendly female dog that you can let socialise and see if she will teach him how to play? Or use that dog to practice saying hello then coming back to you for a sit etc? It could be that he doesn't know how to play or how to interact appropriately. If thats the case, then confident but not dominant/aggressive dogs might be the only way for them to teach him whats appropriate and whats not.