Peeing has nothing to do with being reactive, don't listen to anything regarding "dominance theory" as it has not only been disproven in dogs but also in wolves where the idea came from.
If your dog is reactive you need to figure out what causes him to react and work on that, it can be dogs, people, traffice etc etc and there are ways to manage and train reactive dogs. I have a dog that was dog reactive(fixed by upping his socialisation with other dogs) and is reactive to men wearing hats which i manage by simply not letting them get too close, he's fine with them being around until they try to go near him so i don't let them near.
Of all the areas that have got me confused in my 4.5 months of rescue dog ownership, I think this one is getting the prize. i have a reactive dog and we're doing really really well I think, huge progress with ignoring other dogs recently. 95% of dogs are now not an issue as long as I have sausage.
I'm aware that the techniques I'm using are distraction rather than changing core behaviours (BAT, I guess) but I think they're right for where we are at the moment. It's early days after all ( cuebill & redwing...)
However, loads of people have told me I need to stop him marking as this is part of the reactive behaviour. He does seem to be extremely frequent and persistant in his marking but I don't really know as I've got no benchmark. Most of the time nothing seems to come out which is no surprise as he would need some huge internal tank!
I've googled marking and just got totally confused. Dominance? Territory? communication? Stress relief? Lots of red rags there I know!
So, dominance debates aside, I guess my question is: should I should let my reactive dog mark as he pleases when out in fields (ie not obvious antisocial targets like next door's gate) or is there a reason to encourage him to stop? If so, my next question would be how do I stop him?!