Why Gustang hates "V"?

When "V" appeared, I am sure we all thought they would help each other or at least make an alliance because they have the same goal and everything but Gustang said that "V" is on his hit list now which made me confused.

I thought "Why would Gustang do this?". I saw some theories about Gustang hates V's guts or something about his personality but is it that big of a thing considering Gustang's goal is to end all the other family heads and Jahaad?

And instead, he even puts V on his hitlist. That made me think " there is something up that is more than just hating his guts."

So I researched some stuff and found out, Gustang was actually very close to Arlen. So that made me conjure up a theory.

What if climbing up the tower has some very big consequences, And despite that "V" wanted to climb. He took advantage of Arlen's love for him to bring her to his side and help him in some way to reach that goal.

Remember according to FUG, V was a victim of Jahaad's tyranny and everything but that was because they considered "V" as their God and so they removed the wrong stuff that V had done to make a feasible story for Bam.

What if Arlen hated Bam not because of what Bam is but because she realized what "V" had done?

This is also why Gustangs hates "V" so much so that he put him on his hitlist and saved Tramaurei from him as if "why let a piece of trash get what he wants by killing the other piece of trash".

Well that is just my theory, what do you guys think?