They already explained multiple times that the doctor is in control of all the guides and he can cause the espers to lose control, which would basically be a horrific for everyone. That's why they need to stop him before the deadline
that’s why jus kill him yolo headshot or something
They don’t know if he has a trigger that goes of if he dies that will kill the guides. They don’t know if he will kill all guides if he suspects them of going after him. They don’t know if they are fast enough to kill him before he takes revenge by killing all the guides. If they fail to kill him, since he is a very strong esper, they know he will kill all or at least very many guides. So no, they can’t just kill him.
Exactly they can't just kill him yet which is why they have to play along, but they managed to find a loop hole by sending the espers out of the country. I'm so tired of people wondering why they can't just kill the doctor
Stay being tired cus it’s never that serious
Why can’t they jus killed the old dude yolo