When you say he didn't like some men was he just wary of them or trying to get to them for a nibble? The one I had was a decent guard round the house but normally ok out in public but he wouldn't let you touch him if I wasn't there. We passed one bloke in the road while I was running him along the bike and the mutt was desperate to get him and was still pulling to get back to him half way down the road so god knows what triggered him but he wanted to bite that bloke. I wonder if he had been on my property while we were out and the dog remembered him or something