Sometimes excuses are true, but plausible excuses for not making progress (like those of your interns) are different from the extraordinary excuses needed for p

Sometimes excuses are true, but plausible excuses for not making progress (like those of your interns) are different from the extraordinary excuses needed for persistent and objective actively harmful behaviour. These patterns of bad research tend to go on for a while because the involved people might be powerful and in any case calling them out requires effort and exposure, not because discovering that unreasonably defensive behaviour hides bad research is a surprising "twist".