Hm, thinking some more. Nothing solid, just musing to myself.

Word that keeps coming up in the sketches and rps with Tara for both Discord, Scorpan and Tirek is “Monster,” with emphasis on identity.

Choices between forcefully taking and changing the rules to only fit you, or sacrificing how you act to fit someone else’s.

Tirek seeing anything else as an enemy and against him, further emphasized by his brother betraying him and befriending a pony.

To him, Discord is just as weak and not worth trusting since he already befriended a pony as well. Discord sacrificed who he was originally to become friends with them and was easily swayed, only really proving Tirek’s point.

Discord, having a similar past of imprisonment to a degree can emphasize and understand Tirek’s words of freedom.  Reformed Discord cannot express himself fully like he used to. (Problem being both of them were harmful in how they did that.)

Tirek refuses to be “ruled” by any sort of friendship. It is weakness, and he used it against Discord AND Twilight.