Criticism or badmouthing?
"Criticism" used to mean to discuss something that is important / critical, but now it's just another word for badmouthing and revealing one's shame.
I don't think that people mind at all at discussing important things, even with people outside the group.
Problems arise though if people start badmouthing and revealing one's shame.
Nothing good came out of badmouthing and revealing one's shame, unless of course if your intention is to make people fight each other.
It should be noted that there's no need for let say group A to comment to let say group B ways for group B to improve its conditions, unless it's also in the interest of group A.
Of course, if group A start saying nasty things about group B, you think that group B will just stand there? Chances that it will ignore any comments from group A, or even worse, start a war against group A.
It's not in group A best interest either to say nasty things about any group, unless it's a political move of group A or group A is just a mere puppet to say anything by the puppet master even if it means making the puppet doing a suicidal move.
In general, people are very selfish people, they don't say things to other people unless it will also do good to them, it's a symbiotic thing.
Now... If people start criticizing a.k.a. badmouthing other people and argue that it's not in their best interest to do so, one must be wary if there's a third party involved here that is trying to make people fight each other.
As for 'foreign criticism'.
Ha! That's a laugh, we know that all the world governments are under one ruler, there's no such thing as 'foreign'. The only 'foreign' in 'foreign criticism' probably is in the species definition.
Based on experiences, 'foreign criticism' is just another way of saying, this is one of the many ways to make people from many different countries fight each other.
As for me.
Personally, I don't like at hearing or reading people badmouthing, either at my own group or other people's group.
Remember the saying "If you can't say anything nice, don't say anything at all"?
Well... People should do more of that, and less "if you can't say anything bad, don't say anything at all".