MC: To be clear, this is a request not a command
TL/N: That feels like a pretty loaded "request", huh
Kind of, but not really. Sure it puts an immense ammount of pressure on these applicants, but no more then the seriousness that this responsibility deserves.
If you are building a team whose goal is to defend the earth from a threat that could destroy it, you should never press gang in your combatants.
You also want to eliminate as many weaknesses from your team as possible. Fair weather friends, glory seekers, and any number of troublesome individuals will only cause issues down the line.
So if they are truely serious in this endeavor, they need to be consistently and constantly screening their combatants for the negative traits that could potentially derail their efforts to defend their home.