From the external PoV; it's not okay because it hurts other people, and sometimes people just have no way to separate other's successes with their own failure. In some ways, people who are proud with themselves and aren't afraid to mention it are inadvertently sending a message of 'you're a loser, loser, loooooooooooooooser' for other people.
It's a factor of self confidence from the listener.
But of course there are grey areas as well... For example, when one's performance in work are being praised by their superiors.
Wouldn't expressing even the slightest pride in that case feels like rubbing salt to an open wound?
And even worse / grayer, if one of the other coworkers feels like they are working as hard?
And even grayer, if they actually work as hard?
I think it depends on what someone is looking for.
If they are looking for group harmony first, pride is admittedly one hell of a landmine. There's only a thin line that separates pride and boasting and that thin line sometimes shifts.
On the other hand, @
Kgal is right; society is pushing people to be meek.... then they pushes the same people to be a douche by expressing their pride in an explosive way.
I know you put some context into it, and I'm going to reply on it asap...and without quoting.
In your situations, I can see that it's; yes, most likely adults feeling threatened.
It can be a matter or power as Kgal said. On the other hand, it might be reaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaallly practical: The parents don't want their children to nag at them.
"Mommy! X is going to [insert tons of fun here, ending with an unicorn riding to Santa's home]. WHY CAN'T III??????"
And another hypothesis of mine: it can be that they are irritated with the fact that one of their members are moving to somewhere less crappy (think about it like this: You realized the fact that the group is crappy.
What are the chances that other members also realized that?
What are the chances that your son talking about all the interesting things he's going to do is going to make other kids realized just how crappy their situation atm?
And what will they do if not going to their parents?)
To reiterate : No, I don't think it's your fault in particular. But people just got hurt.
I'm sorry that you and your son had to experience this kind of power play though, especially your son. This is not his fault at all, nor is it yours for moving.
If all else fails, I hope you and your son had fun in your new place.