Corker and Flake haven't got along well with Trump lately (understatement), so this may indeed be a case of begrudging people leaving with the customary parting shot.
But I mean, sheesh, can people not appreciate the context here? Have they not seen all the guff that comes out of Trump every day? Did they not view this story in light of Tillerson's "effing moron" comments (allegedly), or Paul Ryan's Trump roast last week and his recent comments, or the rapid turnover of various senior White House staff, or the "suicide pact" between Tillerson and two other senior secretaries?
http://www.dailymail.co.uk/news/article-4949298/Under-fire-Tillerson-forced-deny-rift-Trump.html
http://www.newsweek.com/rex-tillerson-still-wont-deny-he-called-trump-moron-685477
https://thinkprogress.org/paul-ryan-donald-trump-tweets-ignore-21de72af5d19/
It's not clear what the fallout from this will be but if Trump continues to demonstrate that he lacks any kind of diplomatic streak then he'll also continue to lose support from his own party, not just those -- like me -- who hated him already. It's hard to avoid the conclusion that many who work with him in positions of power and responsibility do so primarily because they have to, not because they want to, but that tolerance is difficult to sustain forever.
Still, I expect Trump will weather this storm. He always does, somehow. The key tests of his authority are likely to come next year, in eg the midterm elections -- which, sadly, already favour Republicans so that may protect him and his party from electoral disaster.