You'll probably not be shocked to learn that I agree with Adam about this. My agreement is on three grounds: 

First: If you want simply to tell — if you have a direct blunt message that you want to get across — there are genres for that: genres of expository and persuasive prose that have developed over the centuries for the specific purpose of communicating clear and straightforward messages. Whenever I read a didactic novel that tells me everything I am supposed to think about the story, I always think: Why did you write a novel, then? You’ve got all these “characters” and “events” getting in the way of your message. You’re not making your message better, you’re just making your story worse. Stories are best reserved for experiences and thoughts that simply won’t fit into the structure of an argument — this is, I think, what T. S. Eliot meant when he said that Henry James had “a mind so fine that no idea could violate it.” Eliot thought James distinctively attentive to those aspects of our experience that can’t be condensed into a solid idea. 

Second: If you know precisely what message you want your story to convey, then your story almost certainly will never convey anything more than you explicitly intended. Which is to say, you will never learn anything more from writing it than you knew when you started. For writers who think they already know everything there is to know, this may not be a problem.  

Third: If you know precisely what message you want your story to convey but are a little too artful, make it too lively, then your readers may draw conclusions you don’t want them to draw — see the experience of Bertolt Brecht as related in the final paragraph of this post. That gives you an incentive to make your story as rigid and simplistic as possible. Which means, again, you’re not making your message better, you’re just making your story worse. 

Finally, I think it worth noting that this critique of show-don’t-tell appeared on Twitter, which is populated largely by people who are vigorously hunting heresies and people who are desperately trying to avoid being labeled as heretics. I can’t bring myself to read the replies to Tade Thompson’s original tweet, but from Adam’s description it seems that many of them are more hostile to “showing” than Thompson is (after all, he allows writers sometimes to show). Being on Twitter might be the worst thing writers of fiction can do, because it habituates them to the fear of Error and promotes practices of declarative belligerence. It makes them terrified of any experience that can’t be condensed into a solid idea; and that diminishes them as writers and as persons. 

In a 1939 poem called “Our Bias,” Auden contrasts human beings to a lion or a rose — those creatures that simply are what they are and can’t be other:  

For they, it seems, care only for success:
While we choose words according to their sound
And judge a problem by its awkwardness;

And Time with us was always popular.
When have we not preferred some going round
To going straight to where we are?