Munsters can be very defensive of themselves, their yard, their truck, their owner, etc. They are often very intolerant of other dogs’ poor social behavior, such as excessive butt sniffing and being jumped on. 
Some Munsters are only a little bit snarky with other dogs and some are a lot snarky. There’s really no way to know which you are going to get. It starts showing up around 5 months of age. It is only with dogs they don’t know well, so the other dogs in their “pack” or that live next door don't cause a problem.

The behavior is always worsened by being leashed, because they cannot get away and feel trapped. A Munster who would be very snarky with a particular dog in his own yard will completely ignore that same dog while out in the field. I’ve never known of a Munster who would not hunt nicely with dogs he doesn’t know well. But you best make sure the other dog doesn’t try to steal a bird out of his mouth while he’s retrieving and you’ll want to leash him up when the hunt is over so there’s no scuffles at the truck over the dead birds.

In my opinion, this is a trait that can be easily “managed,” but you must be aware of what is happening and why so you can avoid problems. You must well-socialize your Munster puppy with dogs of all sizes and shapes so he will be as good with other dogs as possible. And you must let him know bad behavior will not be tolerated.

You must keep him leashed when strange dogs are around and you must watch for dogs that are off-lead and might rush up to him. My dogs have become accustomed to all kinds of dogs running into our yard when people come to hunt/train, so they are prettyy tolerant if I am with them. They know they will be in trouble if they get too snarky. KD will growl a bit and posture, but she’s never bitten or fought with another dog. Still, I would never let a strange dog run into our yard without me being there.