My neighbors don't like me very much

i know right? if you can't raise your dog to NOT be some idiotic chaos monster hen you shouldn't HAVE a dog

Right, because a dog that follows its instincts is a complete monster. How exactly do you propose they train a dog for this specific situation? Why not ask the better question of "How the hell did the dog get anywhere near the neighbor's guinea pigs to begin with?" Last I checked those are usually kept in cages, not free range in the backyard, which means it would be particularly hard for a dog to break out of their own yard, into the neighbor's house, and then into a cage.

Exactly. He's a lab. They're hunting dogs, that's what they're bred for. My question is where did the neighbors keep their guinea pigs, if it was so easy for the dog to get to them?

I have a few guinea pigs, mine are kept inside (cause its hella cold where I live) but I know that some people keep theirs in outdoor hutches. That might be the case here.