What Works For Dogs
When it comes to behavior, dogs always do what "works." If snarling and nipping allows them to avoid trims, they will practice that behavior. If pulling on the leash allows for more forward movement towards a tree to sniff, they will practice that behavioral. If growling at guests causes these perceived intruders to back away, they will practice that behavior. If pushing and whining at the back door gets you to open it faster, they will practice that behavior. If jumping up on you gets them attention (even scolding is attention), they will practice that behavior.
With every choice they make, dogs are creating the life they most desire. You can't blame them, right? The pursuit of happiness was written into our constitution! All beings (humans included) seek to pursue pleasure and avoid pain. It's kinda what keeps things going here on planet Earth.
More often than not, the life your dog seeks looks something like ultimate freedom. A life where human love and affection are free flowing on tap, where boundaries and limits are nonexistent, and where every impulse can be indulged.
When we respond to our dogs in a way that allows them to get to the desired goal, we are implicitly agreeing with their limitless, boundary-free lifestyle. It's kind of like we're saying, "Yes, the world is a bountiful, abundant, and completely safe place to be. Nothing should impede progress towards your goals. Go forth and be free! Don't let me or anyone else stand in your way!"
Unfortunately for dogs, this abundantly free lifestyle is often incompatible with the lives of the humans in charge of them. Dogs who growl and bite their owners often get put down. Dogs who pull on the leash make for an uncomfortable (or dangerous) walk, and as a consequence fewer of them happen. Dogs who jump injure humans and get surrendered to shelters, where they are (predictably) not the most attractive candidates for adoption. It's just the way the cookie crumbles.
So the next time you find yourself frustrated by your dogs behavior, ask yourself if what works for him also works for you. If you find that your lifestyles are incompatible, know that you have the power and the responsibility to change that. It all comes down to telling your dog "This isn't working for me."