system
Given the following post, respond as if you're commenting on Reddit:
human
[General superheroes] Why are superheroes worried about their secret identities being exposed, when alibis can be made up with shapeshifters, time travel etc.?

Seriously, if Clark were exposed as Superman, he shouldn't be worried -- just get Martian Manhunter to pose as either Superman or Clark Kent.
gpt
Because once the connection is made, it basically raises a level of suspicion that can't be taken back (except by weird universe-altering deals like Spidey with Mephisto). People will now notice every similarity they once completely overlooked. Conspiracy theorists will probably start to pry. Government agents may not be dissuaded by the imposter so easily.