It is totally not justified. The AFP itself said the Mautes are down to 60. So, in other words, the people of Mindanao would be inconvenienced by Martial Law just to neutralize the 60 Mautes who are cornered in Marawi? That's just a whimsical misuse of power. Then again, I have already forewarned the public of Duterte's authoritarian tendencies and this is another proof of it.
Source: Senate of the Philippines