Rep. McCarthy was not shadow banned, his Twitter account was misconfigured to hide postings
By: +David Herron; Date: August 19, 2018
The tweet Rep. McCarthy referenced, from Fox "news" host Laura Ingraham, was shown to McCarthy as "This tweet is not available because it includes sensitive content".
Technically that behavior, if this were imposed by Twitter, is not shadow banning. In shadow banning, nobody knows the person has been shadow-banned: Instead they use the platform as always, but other users have a hard time finding that user's content. In this case McCarthy saw the content, but it was blocked from being seen.
Why was Ingraham's tweet blocked from being seen? It was due to settings on McCarthy's Twitter account. Twitter did not take any action other than to respond to a setting on McCarthy's account.