Tail wagging doesn’t automatically mean happy or relaxed. There are lots of different types of wags. For example:The 2 dogs at the end are praised for repelling the intruder.(?) Looks to me like they're both very happy (tails upright and happily wagging) and may be actually trying to jump up on him to get/give kisses.
They're probably just smart enough to realize that he's not a real threat and are joining in on the fun!
“When a dog wags his tail very fast while holding it vertically, he may be an active threat. Remember that a person can get bitten by a dog that is wagging its tail!”
While dogs do not speak the human language, they still communicate quite effectively and tail wagging enhances their ability to communicate. Position and speed of tail wagging takes on different meanings. Interestingly, dogs do not talk to themselves. They will wag their tails in front of humans...
Even “kisses” can be misinterpreted. Some of Peggy’s biggest, most frantic kisses are a sign of stress.