Kids that grow up with shouty parents tend to think it's normal because it is to them. I think it's highly doubtful your grandson will be harmed by being shouted at especially as his dad follows it up with cuddles and then talks in a more normal tone. The best way to deal with it is by staying out of it.
I have a lovely family and am lucky enough to have 2 beautiful grandchildren. The oldest little one is almost three years now and is a typical toddler - never sits still for a minute, always up to tricks and can try the patience of a saint. However, he is adorable and is obviously just learning about the world and how to behave. He is so loved by us all, is mostly a gentle, quite shy wee boy and I can honestly say I have never raised my voice to him and try to show him right from wrong in a calm measured way (it's really hard sometimes as many of you will know).
My son in law is a great guy and works hard, pulls his weight at home with the housework and the children and really enjoys being a kind and caring daddy.
My worry is that he has quite a 'short fuse' and I have witnessed him on a couple of occasions losing his temper at the 3 year old and shouting at him. This has resulted in my grandson running out of the room, crying and upset. Daddy then tries to make things up to him by cuddling, etc as he has then realised he has over-reacted. My son in law seems to think my grandson should understand that no means no and should take a telling, but I feel he is expecting too much from such a young child who is just learning right from wrong. Mainly I hate when he raises his voice like this at such a young child and feel that it is totally unnecessary.
I get upset when I see my grandson getting a 'row' in this way, but do not interfere as I do not want to cause any bad feeling. On the few occasions I have witnessed this shouting I have not told my daughter as I do not want to upset or worry her either.
I feel my son in law is just 'learning' himself how to be a good daddy, but finds it hard to control his frustration and temper sometimes. I feel sure this is not an everyday occurrence, but I worry if being shouted at in this way, even if only occasionally, could have a detrimental long term effect on my grandson. I feel it is unacceptable for my son in law to shout in this way at such a young child and wonder about the best way to deal with this. Any positive advice would be welcome. Thank you.