I want to disrespect a student who died supporting a terrorist group
Why would you try to hurt someone who is already dead?
Because I have zero respect for the dead.
Show respect to people who have died by not saying anything bad about them. Since dead people can no longer hurt us, or defend themselves, it is better to forget their bad actions and remember only their good ones.
But people need to know that he was a bad person.
It is not something that you should even be worried about at this time. He is dead, we should try not to speak ill of him.