Snowy doesn't obey him in the earlier books, and Black Island is a classic example. I've had to slap my (pampered) dog a few times when she doesn't listen to me: she's tried to rip open a trouser-pocket once because it smelt of some breadcrumbs, and other times she's tried to eat chocolate, and after a hearty telling-off, she doesn't do those things anymore. If you had a dog, would you like it if it kept running off to eat or drink things it shouldn't?
Well, it is true that I've never had a dog. My family has always had cats instead of dogs, so yeah... But I don't believe that I would ever slap
a dog, but I would find other ways to discipline it. Then again, I might be too soft to be a good dog owner. Cats work much better for me. Because even though they too might need a hearty telling-off sometimes, they are much more independent than dogs and need less discipline to be a functional pet.
Abdullah is a spoilt child, and I do understand the times when Tintin and Haddock smacks him on the bum in Black Gold: he didn't understand the serious situation he was in, and he behaved so ungratefully to his rescuer - I remember another member writing, in the forums, that it was more like a case of rescuing Muller from Adbullah! He deserved it.
Yes, Abdallah was a spoilt child. But I don't see how him being smacked on the bum changed any of that. As a matter of fact, he was just as bad as ever afterwards. But I can see that from a 1940s perspective, this would have been an acceptable way to deal with a situation like this one. But if the exact same story was written in Belgium today, I don't believe that good guys like Tintin and Haddock would ever have smacked a child. Even if the child was a spoilt brat.
However, I do agree with you on Congo - there was no proper justification for slaying all twelve antelope (why couldn't have he bought food from the village where he hired Coco?), and killing the gorilla and elephant was just cruel, not to mention the "exploding rhino".
Well, when it came to the antelopes, Tintin believed that it was a single animal, that he didn't seem to be able to kill. So I don't believe that he meant to kill so many antelopes. But still, it is hard to see anything funny or even interesting about such a scene today. And as for the rest of all the scenes in "Congo", where Tintin is killing off animals, they are (if possible) even worse than that from a modern perspective. I'm so glad that Hergé at least let that poor rhinocerus survive in some newer editions, because blowing an animal up with dynamite sounds just stupid and needlessly cruel.
As for a justification for these scenes, they were not seen as offensive when that story was first written back in 1930. It was perfectly legal to hunt like this in Africa at the time, and it was very common for Europeans in the colonies to act like Tintin did. And honestly, I can't remember being bothered by these scenes when I read "Congo" as a child. But I struggle with them very much these days as an adult, even though I know that we have to look at them from a historical perspective.