I see your point, but I disagree in this situation. If there was no context around the discussion, you'd be exactly right. But there is context, and the context is the immigration ban put in place by the president. That immigration ban excludes people from specific countries. This article was very obviously written to show how important immigration is as a way to counter the reasoning that bore the immigration ban, but I feel it cheapens the point when you include immigrants who are not part of the ban.
Basically, if the point of the article was just "immigrants are good", then yes, you're right. But since the point of the article is "this immigration ban is bad!", it makes sense to restrict the discussion to people from countries actually listed on the ban.
To put it another way, what if the article mentioned Canadian immigrants, South African immigrants, German immigrants, British immigrants.... but no Iranians? No Syrians. No Iraqis. The conclusion of the article could then be portrayed as "see? muslim immigrants don't do anything useful anyway! ban them!" For every immigrant you put in the article that isn't affected by the ban, the case for the ban becomes stronger. That's why I think we should limit our conversation to the context implied by the article's conclusion.