Can anyone explain why joshua wants to kidnap grayson?

To to make him talk with Chase (with a little beating lol). He wants both of them to have a conversation so that it would help chase

in chase story he want to help chase get a revenge to greyson







spoiler
the revenge is not successful but greyson finally can learn emotion and apologize to all his victim and the last is chase . but chase not forgiving him and run away from greyson pursuit