Kids today grew up with the internet - knowing that big corporations we're slanting views/news from day 1 because they could go compare the same headline at fox, cnn, and nbc. Previous generations couldn't do that so easily. So a complete distrust of news shouldn't be surprising.. they aren't really very trustworthy in the first place.
These teens don't need to trust the instagram accounts, which is the whole point. The account just makes a post to bring up a discussion point, whether or not that point is fact-checked is irrelevant. (Its mostly gossip with political/moral/idealogical/etc angles anyway)/